This talk from pediatric nephrologist Sanober Sadiq, MBBS, offers a deeper understanding of hydronephrosis, a condition affecting 1 in 100 pregnancies and ranging from an essentially benign problem that resolves on its own to one requiring surgical or other interventions. Sadiq covers possible causes of a swollen, non-draining kidney; systems used to classify hydronephrosis severity and how the grade impacts treatment decisions; imaging modalities from routine prenatal ultrasounds to nuclear medicine scans; antibiotic use; and which cases to refer as well as how to know whether urology or nephrology is the best choice.
Hi, everyone. Um, thanks, Maria for the introduction. Um, I'm Sanoar Siddiq. I'm one of the pediatric nephrologists that works at UCSF. I do my satellite clinic in Fremont and in Monterey, and then I have also my clinics in Mission Bay. Um, the topic that I'm going to talk about today is assessment and treatment. Hydronephrosis, and the reason for doing this talk is, firstly, um, I know you guys see a bulk of patients who have hydronephrosis, and it's also sort of a gray area as to who to refer to is should it be nephrology or urology, and so I just wanted to provide some education on that. And so I'm going to get started uh with the objectives. So the objectives of my talk are, I'm going to spend a few minutes on um renal development as to how the kidney is formed, um, and then review the incidence, etiology, and relevant findings for hydronephrosis, um, then delve into classification system for hydronephrosis, and lastly, talk about the management guidelines. So, renal development, it starts in the first trimester, um, around 9th to 10th week of gestation. It consists of pronephros, mesonephros, and then metanephros. And the pronephros, mesonephros, they form and then involute and it's actually the metanephros that develops into the functional final kidney. And this is how it looks like, um, that the metanephrosis, it forms into the ureteric burt and then the metanephrogenic blastoma, and in turn, it forms into the, um, uh, the, the ureter, the pelvis, um, and then the major calyx, the minor calyx, um, the collecting tubules, which includes both the proximal, um, the distal collecting tubules, and then the loop of hind leg. So as I mentioned before, um, the first glomerula or the, the kidney filter forms at about 9 to 10 weeks of gestation. And then the development continues, but then there is an exponential increase in nephrons, um, between 18 and 32 weeks of gestation, and then the nephron development completes between 32 to 36 weeks of gestation. So that, that's why anyone born before 36 weeks of gestation, we can, we think about them as having low nephron mass, which puts them in, uh, at risk for complications. Which include ah being at more risk for um acute kidney injury or um having, developing hypertension, um, or other kidney complications. So, secondly, I'm going to talk about the incidence and etiology and then relevant findings for hydronephrosis. So, what is hydronephrosis? Um, it is the dilation of the renal collecting system and it is most commonly diagnosed on antenatal ultrasounds and, um, it's sort of, it's getting more, more routinely diagnosed now because everyone gets antenatal ultrasounds done. Um, it can be benign or, or, or I would say I call it as transient or it can be associated with significant congenital abnormalities of the kidney or the urinary tract, and the incidence is 1 in 100 pregnancies or 1-5% of all pregnancies. Um, the causes for, um, hydronephrosis, so the most common one is transient hydronephrosis and the incidence being 41 to 88%. Um, the second common cause is the urethropelvic junction obstruction, uh, the incidence being 10 to 30%, vesicourethral reflux being the third common cause with incidence being 10 to 20%, urethrovesicle junction obstruction, the incidence being 5 to 10%. Multicystic dysplastic kidney, the incidence being 4 to 6%. Posterior urethral valves, um, which is one of the more, um, uh, concerning reasons for hydronephrosis, but, uh, the incidence is low, being 1-2% or urethrocele ectopic urethra tuplex system, um, the incidence being 5 to 7%. So transient hydronephrosis. It's um it's basically, it's seen on the antenatal ultrasounds, um, and there is history of renal pelvis or calluses dilation, and it is mostly related to narrowing of the urethra pelvic junction or there are just natural kinks or physiologic kinks that occur or folds that occur early in development. And usually for these patients, it's, um, it's getting a postnatal ultrasound when they are greater than 48 hours of age, and then assessing what the hydronephrosis, um, what, what is the, what is the staging of hydronephrosis at that time. In my experience, usually transient hydronephrosis This takes about approximately 1 to 2 years to resolve, but it, it, it is, it is not associated with any kidney injury. It is not associated with any urine infections, and as it is transient, it resolves on its own and basically just requires um serial um ultrasound screening. The second common cause, so the urethropelvic junction obstruction. So this is, there is pelvic calicial dilation present, but there is no ureter dilation present, and this is like the key mark uh for, for UPJ obstruction. And it is commonly unilateral, um, and this is, uh, if, if these findings are present, then they are highly suggestive of, um, UPJ obstruction. Um, in most cases, it does not require any management, any surgical management, but surgical intervention may be needed in 32 to 50% of these cases. Um, and in cases where no surgical intervention is needed, it's mostly about, you know, medical management, monitoring them, um, ensuring that, you know, just educating patients about, um, urine, uh, urine tract infection prevention. Um, and so, this is how it goes. Um, the third common cause for hydronephrosis is vesicourethral reflux. So this is, as the name says, it's basically retrograde passage of urine from the bladder into the upper urinary tract system. And the management of this, um, is basically, it's just monitoring antibiotic prophylaxis and surgical correction as needed based on the, uh, based on the, um, uh, the, the grading of the, uh, vasicourethral reflux. So this is what the classification looks like. So there is um grade 1 to 5, um, and this is Uh, the gold standard for diagnosing vesicourethral reflux is voiding cystourethrogram. So this is how the grading is done on BCUG or voiding cystourethrogram. So grade one is the, uh, is reflux that is limited to ureter. So there is, um, no dilation present. It's just reflux that is going into the ureter. Um, grade 2, it's reflux into renal pelvis, but without pelvicalacial dilation present. And then grade 3 is mild dilation of the ureters, so now the ureters look a little thickened, and then there is also pelvicaliceal system dilation present as well. And then grade 4 is blunting of the fornaces, but preserved papillary impressions which are towards the periphery. Um, and then the ureter is dilated moderately, and then it also looks more tortuous. It's not straight anymore. And then grade 5 is loss of furnaces and papillary impressions. So now, the, the papillary impressions are not visible as they were before. And then there is severe dilation of the pelvicalacial system. The ureter is also more tortuous and then it's more severely dilated. So this is what the grade 5 looks like. I'm going to share another um uh slide uh with just how it looks like on the voiding cystourethrogram or VCUG. So, starting from the far left and going to the right, um, so this one is grade 1. and then, um, on the same picture, on the same picture A, um, the one on the right, that's grade 2, moving to picture B, so one on the left is grade 3. Um, and then the one on the right is grade 4, and then picture C shows how dilated it is and it's grade 5. The prognosis of vasicoureterral reflux, so spon uh and this is like one of the questions that parents always pose if their kid has vasicoureteral reflux. So, grade one and two, the spontaneous resolution chances are pretty good. They are greater than 80%. For grade 3, it is 50 to 80%, and then it slowly goes down, uh, with the grades. So grade 4, it's 35%. With grade 5, it's less than 15%. Um, this study, which is also known, um, so vasic ureter reflux, I believe, is one of the most, um, most, uh, the, it's one of the topics that has been studied, um, a lot. Um, and so, the reverse study was done, uh, and reverse stands for randomized intervention for vasicoureteral reflux. So this was a very Large multi-central trial, um, double-blinded, um, study, um, that was done in 607 children to assess the effectiveness of using antibiotic, which was trimethoprim sulfamethoxazole, um, and comparing them with placebo, um, in kids who had BUR over a 2, over a 2-year follow-up period. Um, and what they found is that children who received, um, the antibiotic or the trimethoprim sulfamethoxazole were less likely to have recurrent febrile or symptomatic UTIs. Um, what they also found is that children with grade 3 or 4 vesicourethral reflux were more likely to have febrile or symptomatic UTI than those with grade 1 or 2, which makes sense, uh, based on how, um, how dilated the urinary tract system becomes in grade 3 or 4 versus how it was in grade 1 or 2. And then the Uh, the patients who received the antibiotic, um, compared with placebo, um, this was a significant finding. It did not reduce the incidence of renal scarring, um, uh, in patients who received the antibiotic versus those who received the placebo. They also found that among children with recurrent E. coli UTI, um, Bactrim actually was increasing the risk of Bactrim resistance, and it was closer to 63% versus, um, just, um, 19%. And then the assessment by VCUG done at two-year follow-up in about 400 patients demonstrated resolution of reflux in 151% of patients. Um, there was improvement in 23% of patients. There was no change in 19% of patients and then worsening of reflux was seen in 7% of cases. So moving on to the fourth common cause, which is the urethro-vesicle junction obstruction. It's different from the ureter to pelvic, which is basically blockage that happens at uh at the ureter and the renal pelvis level. This, in contrast, is a blockage which happens at the ureter and the bladder junction. Um, and so basically blockage where ureter meets the bladder and so it is associated with dilated ureter. Um, and, um, uh, of course, um, it's what. Anyone, uh, it put patients at risk for, um, urine urinary tract infections. Um, how it is diagnosed, so basically, um, anyone who had, um, uh, prenatal hydronephrosis present, and then in older kids, uh, they can present with flank pain, stones, or urinary urine tract infections as I mentioned. Um, it's usually we start off the workup, uh, with the ultrasound and then moving on to VCUG and then thinking about nuclear imaging or scans in, in, uh, like MAC 3 or, um, thinking about MRI. Um, the reasons for this is it can occur during development, as we mentioned, as I mentioned before, um, one of the congenital causes, but there are other causes too, which includes scar tissue, um, infection, polyps, stones itself can cause urethrovesicle junction obstruction, which, of course, um, uh, can happen. Um, and so anyone who also present with stones, um, that's, that's one of the reasons for getting ultrasound and also thinking about is, you know, uh, is this the reason, um, uh, for, um, it can, as it can cause both stone formation and then it can also cause, uh, it's one of, stones is one of the reasons for UVJ obstruction. Um, and then most patients who are born with UAJ UBJ, they resolve over time and do not need any surgical correction. Um, they do need to be followed to train creatinine and then assess, um, uh, what their level of continence is. Um, I will keep this one short because this is multicystic dysplastic kidney. So, um, it is basically presence of non-communicating cyst of various sizes and, um, and there is no, um, evidence of identifiable renal parenchyma. So this is essentially a non-functioning kidney, um, and, um, it can be one of the reasons for causing hydronephrosis. And then posterior urethral valve. So as I mentioned before, the incidence of that is 1-2%, but it's, it's one of the more um serious causes for hydronephrosis that requires very, very close monitoring. So this is associated with um prenatal hydronephrosis. Um, there is dilated thick-walled bladder. And or ureter, um, and then dilated posterior urethra and then there is decreased amniotic fluid. So some of the findings that are seen on the antenatal ultrasounds, and it is basically caused by the membrane remnant in prosthetic urethra in males. Um, It can cause, um, of course, just with the, uh, membrane remnant, it can cause lower urinary tract obstruction and which, uh, which can, which, of course, carries worse prognosis, um, due to pulmonary hyperplasia and renal damage itself from having the decreased amniotic fluid. And so, um, the survival for this, so the 10-year survival is, uh, I mean, it's over 90%, um, uh, in patients who are diagnosed with it in first year of life. Um, and the important prognostic factor is what was the creatinine? Where did the creatinine made her in first year of life? That tells us the most about what, how does the prognosis look like in the long term. The complications, of course, are there is concern for lower urinary tract function, um, so they, um, may need, um, to do long-term cathing. Um, 20 to 65% of patients will develop CKD, um, which could be from just having urine infections too, and then 8 to 21% will progress to end-stage kidney disease. Usually for these Patients, it's uh just about, um, they are, they make urine. They are polyuric, uh, but it's just that they, just with, uh, with their kidneys being formed under so much pressure antenatally, um, they are just not functioning good. So, what, what, so some of the reasons, or one of the reasons I would say that we think about starting them. Dialysis or thinking about transplant is just because their kidneys, um, the creatinine, uh, is not good. The BUN is very high, so their kidneys are not functioning well. Um, they are still filtering OK, but it's the clearance thing that is not good. And so that's why they ultimately, mm, if they, if they were to, they may require dialysis or transplant for that reason. So now moving on to the classification system for hydronephrosis. Um, so this is an area that has changed a lot over time. So, firstly, um, in 1993, there was a Society of Fetal Urology classification. Um, and then, um, they modified it. And so in 2010 came the Society of Fetal Urology, um, anterior Posterior diameter System. And then in 2014, there was a urinary tract dilation system that came up. So, I'm going to start off with talking about, um, the SFU grade system, which is the Society of Fetal Urology grade system, which was in 1993. So over here, they graded it um from 1 to 4, um, and they looked at the appearance of calluses, pelvis, and then the thinning of the parenchyma. So they started off with grade 1 with renal sinus with just with urine, and then grade 2 filled pelvises, filled pelvis with dilated major calluses, and then grade 3 was uniform dilation of major and minor calluses, and then grade 4 was parenchymal thinning. They did modify the system, um, just because, um, there were, um, it was still leading to, um, Uh, it, it was still, uh, it was a little misleading and it was not, um, uh, helping in diagnosing all the cases, uh, of hydronephrosis. So, they modified in 2010, uh, for Society for Fetal Urology, APD system, which was the anterior posterior diameter system. And over here, they were looking at the diameter of the renal pelvis and then based on that, assessing what the, what the grading of the hydronephrosis would be. And so over here, they graded it based on mild, moderate, and severe, and then 2nd trimester and 3rd trimester. And so mild was, uh, on the second trimester, 4 to less than 7 millimeter, um, in the third trimester, 7 to less than 9 millimeter, moderate, 7 to less than equal to 10 millimeter in second trimester, and then in third trimester, 9 to less than equal to 15 millimeter. And then severe was greater than 10 millimeter, um, and then third trimester greater than 15 millimeter. And so, the degree of um hydronephrosis, uh, based on this um grading system, the mild was 56.7 to 88%, so most of the cases, moderate was 10.2 to 29%, um, and then severe was 1.5 to 13.4%. And then lastly came this system, which is the Society for Fetal Urology UTD system, which most of the centers use now, um, including UCSF, um, and over what happened with this one is just because it, it was a combination of everything. So, it included the things from the 2010 APD system, the anterior posterior diameter of the renal pelvis, um, and then it also included the anatomical markers which are present in the 1993 SFU grading system. Um, and so for this one, it was, um, it was implemented after, um, after providers from different societies sat down and then discussed that, you know, this is how the system should be, including everything, the anatomical markers, and then also looking at the diameter. And so these were some of the soc these were the societies or 8 societies that sat down and made this operating system. And so this one basically includes the anterior posterior renal pelvis diameter. And then, um, the calicial dilation, which is the central and peripheral, the parenchymal thickness, the parenchymal appearance, um, the ureter, bladder, and then if there was any unexplained oligohydramnios. So this is how it looks like the anterior posterior renal pelvis diameter. So either uh measuring it from um as they, as they're measuring in picture one or measuring it in picture two and then calyx is central is this one and then peripheral. And this is how the report looks like, um, and it's usually towards the bottom of the report, it says UTD classification, and this is how the radiologist, um, Now graded. It's still not present in all the imaging centers, um, but most of the imaging centers use this grading system now, as I mentioned before. So these are just, just some of the um radiological imaging pictures and it mentions, so the anterior posterior renal pelvis diameter in picture A. Um, they're, sorry, uh, my apologies. There are a lot of picture B's over here, but um this is how the central calicial dilation looks like. And then how the peripheral calliceal dilation looks like over here. Um, here, um, there can be a, a cyst can be seen and there's also parenchymal thinning present and then bladder wall thickness. This is the bladder in picture C. So, um, dividing this up to antenatal hydronephrosis, UTD system, and then there is postnatal hydronephrosis, UTD system. So, the antenatal, um, uh, hydronephrosis UTD system, so it's basically divided into, um, when was the ultrasound done? So, 16 to 27 weeks. So looking at the anterior posterior renal pelvis diameter, 4 to less than 7 millimeter, or if it's greater than equal to 28 weeks, then, uh, the anterior posterior renal pelvis diameter being 7 to less than 10 millimeter. And then looking at if there is any central or there's no taliceal dilation present. So then this is UTDA one and this is low risk. Now, moving on to um the yellow yellow boxes over here. So 16 to 27 weeks with the anterior posterior renal pelvis diameter being greater than equal to 7 millimeter. And then greater than equal to 28 weeks, uh, the anterior posterior renal pelvis diameter being greater than equal to 10 millimeters. Over here, if there is peripheral calliceal dilation present or parenchymal thickness abnormality, parenchymal appearance abnormality. Uter's abnormal, bladder abnormal, or if there's any unexplained oligohydramnios, then that's concerning and they are classified into increased risk category, which is UTDA 223. And I'm going to talk about the management of this in the management guidelines section. Now, um, this is the postnatal presentation, so for the UTD system. And over here, they classify it as based on, um, uh, based on, uh, again, the, uh, basically, the first thing that they look at is that the ultrasound should be done at greater than 48 hours of age. And then the anterior posterior renal pelvis diameter. So if it's 10 to less than 15 millimeter with with central calliceal dilation present, then this is classified as low risk. Ultrasound again done at greater than 48 hours of age with anterior posterior renal pelvis diameter greater than equal to 15 millimeter. With peripheral calliceal dilation present, and then the ureters are abnormal, so then this is classified as intermediate risk. And then, greater than 48 hour ultrasound, um, anterior posteriornal pelvis diameter, greater than equal to 15 millimeter with peripheral callousal dilation present, parenchymal thickness abnormality noted, or parenchymal appearance abnormal, or ureters abnormal, or bladder abnormal. So then that is classified as high risk. So, um, in the antenatal, there are two. they put it as low risk, A1, and then A2 or A3 are high risk. Over here, there are three categories. So UTDP1, UTDP2, and then UTDP3. So, um, how reliable is this classification system since this was, since so much effort and thoughts were put into this. So, um, there, uh, it has been shown to have high agreements between rators and then substantial agreement within rators using the UTD classification system. The most discrepancy, uh, was, uh, was noted for interpretation of central and peripheral calliceal dilation. Um, uh, there was a discrepancy noted within that area. And then the only other thing with this one was, especially the UTTP3, um, since, um, it just fails to demonstrate the severity of hydronephrosis. And so, um, And I'm just going to go back. So, you know, it just has a lot of components into it, and so, um, it sometimes, uh, can, uh, lead, uh, mislead from prompt treatment. So, uh, it, sometimes it's hard to, it's, uh, it can be a little hard to know just from this grading system as to who needs surgical treatment and who can safely be followed non-operatively. Um, but again, This classification system so far has been shown to be the most reliable and so that's why it's still being followed upon. And again, if there is any confusion that is noted on the ultrasound, then we Usually move on to getting other imaging done, um, including a VCUG or um thinking about, um, nuclear imaging, um, to find it out. But again, this is still one of the best screening tools and one of the best screening rating system for hydronephrosis. Um, and so lastly, moving on to the management guidelines for this. Um, so, um, as I said, for the antenatal hydronephrosis, so, um, the antenatal hydronephrosis UTDA one, it's low risk, and, um, I'm just going to move a little back, and this is what it was. So, um, anyone with central or no calliceal dilation, they were low risk. And so moving back again over here. Um, they, uh, it's usually recommended to get another, uh, uh, ultrasound at greater than equal to 32 weeks of gestation. And then after birth, they should get two additional ultrasounds. So, one is greater than 48 hours to 1 month, uh, within that time frame, and then the second one is 1 to 6 months later. Um, and then the UTDA 2 to 3, uh, which was the increased risk category, um, the prenatal period, um, Initially, it should be done in 4 to 6 weeks, uh, from the last ultrasound, and then after birth, um, they should have an ultrasound at greater than 48 hours to 1 month of age. And again, um, it depends on how how concerning the ultras the antenatal ultrasound was looking. Because if there was bladder thickness present or if there was unexplained or unexplained oligohydramnios, or if the parenchyma uh uh was looking abnormal, then they should get an ultrasound earlier than 48 hours, uh, because it may indicate some, something more concerning including posterior thrill valves and may need more urgent intervention. And for these cases, usually, um, uh, they do require specialist consultation including, um, which does include nephrology or urology, and, um, um, we, uh, for these patients, uh, we also meet with the family and let them know about if, you know, for example, this looks like this could be posterior valve, then This may be, this is how things would look like once your baby is born. Um, there is chance for chronic kidney disease. There is chance for, um, um, end-stage kidney disease, and we talk about dialysis, transplant, um, and all those things too. And usually for these patients too, um, it is recommended that once they are born, they are started on antibiotics until they get the ultrasound done and other imaging done, just because they are um at more risk for um any sort of infections. And then, uh, this is the, um, uh, the management, uh, for the postnatal, um, hydronephrosis. So, uh, for the UTDP one, so for this one, it was, um, Um, yeah. So for this one, it was, um, the anterior posterior renal pelvis diameter being 10 to 15 millimeter, um, with central calliceal dilation present, and so this was low risk. And coming back to this slide, um, over here, they do recommend follow-up ultrasound at 1 to 6 months. Um, In our practice, I mean, if they are born, um, uh, It, we do recommend that just getting an ultrasound, um, uh, right before discharge because that is usually like when they are greater than 48 hours of age and it's just easy versus calling them back and getting the ultrasound done. But again, the ultrasound, follow-up ultrasound for low risk, it can be done with Between that time frame of 1 to 6 months. It does not need to be done urgently while, even when they're admitted. It just, it's just, um, easier and more convenient for parents to get it, get it done when their newborn is still in-house, uh, and, and it can be, and as long as it's done greater than 48 hours of age. Um, it is usually accurate and reliable. Um, again, VCUG, antibiotics, and functional scan are most like are not recommended unless there is worsening of hydronephrosis or um there is concern for um urine infections, then it is recommended. Um, and then for UTDP too, so that is the intermediate uh risks. I'm just going to go back. Um, and look into this, um, slide. So, uh, again, for this one, the anterior posterior renal pelvis diameter is greater than equal to 15 millimeter, and for these patients, the peripheral calliceal dilation is present, and then the ureters are abnormal. So that puts them at intermediate risk. So for these ones, the, what the guidelines suggest is that they should get an ultrasound done 1 to 3 months, and for these ones, maybe we do ask to get an ultrasound or suggest getting an ultrasound done while they're in-house, as long as it's greater than 48 hours of age. Um, and then again, depending On what the ultrasound shows, deciding on if they need a VCUG, um, does this look like a vesicourethral reflux, or, um, it requires more information. Um, antibiotics, um, again, it depends. Um, usually, if the follow-up ultrasound, um, I mean, if it shows P2, uh, most of the time we think about starting them on antibiotics, but, um, again, it's sort of a gray area and it depends on what does the ultrasound shows. For example, if the ultrasound does show that the ureters are abnormal, then we think about starting them on antibiotics, um, until we get the VCUG and then decide on. Um, and then the functional scan, I think it depends a lot on, um, also what the, what the, uh, what the VCUG shows, um, and how the patient is doing. Uh, we also think about getting just a, uh, just a chemistry panel on them just to see what their kidney function looks like and then deciding on if they need a functional scan or not. Or for example, if the, uh, ultrasound is showing the dilation, the VCUG is not showing any concern for obstruction, then we're thinking about like if the functional scan, if there may be like an upper level obstruction that's present. And that may be seen by um a functional scan more easily. Um, and then lastly, the UTDP3, which is high risk, which includes all the components. So, uh, firstly, um, the, um, the anterior posterior renal pelvis diameter being greater than equal to 15 millimeters with peripheral calliceal dilation present, with parenchymal thickness abnormality, parenchymal appearance being abnormal, ureters being abnormal, or bladder being abnormal. So they are high-risk categories, and for these ones, it's usually recommended to get an ultrasound. Um, again, you know, as I mentioned before, it's usually if it's very concerning, then getting an ultrasound less than 48 hours of age is recommended, and then, uh, based on that. on when should be the next ultrasound. Um, for these patients, most of the time, they end up getting, yes, they get, they get a VCUG and then it is recommended that they get started on antibiotics and then the functional scan can be decided on later, especially if the VCUG is, um, not showing something or Or, you know, just need more information on how the, the, the, both the kidneys are functioning. Um, so then it is um recommended too. So again, um, uh, we recommend that ultrasound should be done greater than 48 hours of birth because, um, hydronephrosis could may not be detected due to extracellular fluid shifts that are present in newborns and so waiting until then, except for, um, cases where There is bilateral hydronephrosis um associated with urethral dilation, or there is a dilated bladder, um, or with a hydronephrotic, nephrotic solitary kidney. So all more concerning and serious findings than getting an ultrasound done sooner. Um, and then, again, UTI prophylaxis may not be beneficial and low and intermediate risk, and they are mostly reserved for high risk. So, including posterior urethral valves. If there is bilateral UBJ obstruction or if patients have giant hydronephrosis, so basically having like Anterior posterior renal pelvis diameter greater than 15 millimeters. So that's why, um, I think over here, um, the, the P1 and the P3 are clear. I think the P2 is a little bit of a gray area where, you know, it does require more thinking about does this patient need to be on antibiotics or not. Um, and, you know, does this patient need more imaging or not. And then choice of antibiotics are usually, um, um, amoxicillin for less than 3 months of age, so that's what usually the newborns end up being on. And then trimethoprim, sulfamethoxazole or nitrofurantoin for greater than 3 months. Um, circumcision has been shown to prevent UTIs in infants with hydronephrosis, and there was this very big study done which did show that circumcision was associated with a significantly reduced risk of UTI. But this is an area still that is being studied upon, um, and there still needs to be large trials done on this. And so, it is suggested, but again, it's not, it's not something that is mentioned to be recommended to families. Like, sometimes, and that's what, when we recommend to families, some families are just like, oh, we, but we heard that, um, you know, I think the, the families have already done their, um, research on this too, so sometimes they are a little hesitant and they do say, oh, but, you know, it's, it's, it's a little bit of a, a gray area again, like, um, again, it can't, of course, it prevent UTIs, but, um, it's still something that needs to be studied more upon and then, um, uh. Yeah, and then deciding based on that. But, um, yeah, this study that was done in Australia did show that uh it, it was associated with a significantly reduced risk of UTI. And then, moving on to the imaging modalities, so the renal ultrasound, it's one of the most um most best or or one of the best screening, um, uh, techniques because it does not require sedation. Um, it's very easy to get done. Um, it's inexpensive, but again, it provides limited information. Um, the VCUG, it can identify bladder outlet obstruction, um, but with, with this, of course, um, a catheter has to be inserted into the bladder. Which, um, which I have seen in my practice, um, some families or especially moms are a little bit more hesitant, um, just because it can cause a lot of discomfort to insert a bladder into the, insert a catheter into the bladder of a baby. Um, and there is a risk for radiation exposure, but, uh, that's why it's, uh, step, going stepwise, um, is useful, um, because, uh, once a renal ultrasound is not giving, uh, it shows something, but it's not exactly providing us with all the information, then talking to families and, um, they do, uh, then agree on getting the VCUG. Um, also, sometimes, um, at UCSF, the ultrasound and the VCUG can be done together too, so that's something else that, um, that is helpful and convenient, um, for, uh, families too. And then there are these imaging modalities which includes nuclear medicine scans. So, the, the two most common ones that we use um are the MAC 3 scan and the DMSA scan. So, the MAC 3 scan is, is the agent of choice for functional kidney imaging. It helps in knowing like how much each kidney is helping, uh, is contributing to the kidney function. So it should be 50 and 50. Um, and if there is, I think, greater than equal to 5 to 10 point difference, then it can be concerning that one of the kidneys is functioning less than the other one. It is helpful in detecting obstruction and then it helps in evaluating, um, kidney transplant allografts, um, after, um, kidney transplant. And then DMSA scan is, um, it's good for evaluating renal cortex, um, looking for scarring or, um, looking, um, uh, scarring just from the, uh, from scarring from kidney injury or scarring from urine tract infections. And then the last one is the magnetic resonance uro urography. So, um, at least for UCSF I can say we usually don't do this that often. Um, I'm even not sure that if we do it at all. Um, uh, we usually, um, uh, go with the, the nuclear medic medicine scans that I talked about. But, um, it has been shown to provide more superior anatomical and functional information. Um, it's just that it is, um, it does require contrast, and, uh, anyone who has chronic kidney disease or if their GFR is less than, um, is less than 30, um, then the, the, the contrast, it's, which is the gadolinum, um, it can put them at risk for getting nephrogenic systemic fibrosis, which is a skin condition. Um, and again, this, uh, contrast agent, um, it used to happen more, uh, with the older contrast agent, and with the newer contrast agent, they have not seen it, but again, the risk is still present. Um, and again, it requires sedation too, so, um, uh, there, there is swaddling technique, and swaddling technique does work with the babies, but again, if it doesn't, then it does require sedation, which is, again, uh, you know, um, it's just a big, big thing, um, to think about too. So, um, this is actually my last slide. So, um, I, I think this is one of the areas where everyone is, OK, should we refer them to urology versus nephrology? Um, referral to both the subspecialties simultaneously, of course, can cause duplication of work for both the provider and the patient. And so, um, that's why, uh, um, I think that's why avoiding to do that is, um, uh, is, is helpful, um, um, uh, uh, to just not refer to both subspecialties. Um. I think patients, uh, who have, uh, severe bilateral hydronephrosis or they have hydronephrosis that is associated with urethral or bladder dilation, so anything concerning. So anyone with P3, um, or high risk, they should be referred to urology because there is this increased chance that they would require some surgical intervention and Good for them to establish, um, care with urology for that reason. Um, also, patients who have, uh, who are symptomatic, uh, and having recurrent UTIs, um, or, um, developing resistance, um, to antibiotics that they are getting, um, after having multiple recurrent UTIs, um, They should also be referred to urology because there is a good chance, especially with, even with kids who have vesicourethral reflux. Like, even if it's grade 3, but they are getting a lot of urine infections, um, and then they are requiring, um, uh, a, a, a use of a lot of antibiotics, and that puts them at increased risk for resistance, then they should be referred to urology, and that is what we do in our practice too. Um, anyone who have had like, 2 to 3 infections, um, they should be referred to urology because there is a good chance that they would require some sort of surgery to correct that vesicourethral reflux. Um, anyone, of course, who has hydronephrotic solitary kidneys, so they only have 1 kidney, and if that also has dilation, that's concerning and may need to be corrected rather than just being monitored or watched, they should also be referred to urology. Um. For patients who are, uh, referred to nephrology, um, so anyone with UTDP1 or P2 or anyone who had hydronephrosis, and it could be just transient hydronephrosis, they can be followed by nephrology. Um, and the only reason for seeing them outpatient is, um, uh, getting ultrasounds done, um, or if they need any other imaging studies or assessing what their kidney function looks like. Uh, what their creatinine is looking like, um, um, and so someone who can watch those things and it could, it can easily be done by us, um, and I mean, even for us, so in the nephrology group, so anyone who has, um, for example, if I start seeing a patient who has UTDP one and then it sort of worsens or they start having urine tract infections, then, uh, I, I can easily just refer them to urology too. Um, so this is how it can also go. Um, and, uh, from my experience, what I have seen is that anyone who has severe bilateral hydronephrosis, um, as, you know, we get the antenatal ultrasounds done, it's usually it's usually seen and so from that point to the Urology does get involved. And so, um, uh, they are already familiar with the patients too. So, um, I think those are, those are the things, uh, those are some of the reasons for thinking about referring them to urology or versus nephrology. Um, and so, um, yeah, so this is how I would go about with this, um, uh, the referring process.
