Detective Nephron

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Detective Nephron, world-renowned for his expert analytic skills, trains budding physician-detectives in the diagnosis and treatment of kidney diseases. L. O. Henle, a budding nephrologist, presents a new case to the master consultant.

NephronWhat do you have for us today, my dear apprentice?
HenleI have a 77-year-old white woman with a history of type 2 diabetes mellitus and recently diagnosed metastatic ovarian cancer and now acute kidney injury (AKI).
NephronStop… let’s see what we can dissect from that.
HenleYou will be all over this!
NephronNot another onconephrology case, Henle; let’s do some basic nephrology.
Henle

Detective Nephron, world-renowned for his expert analytic skills, trains budding physician-detectives in the diagnosis and treatment of kidney diseases. L. O. Henle, a budding nephrologist, presents a new case to the master consultant.

NephronWhat do you have for us today, my dear apprentice?
HenleI have a 77-year-old white woman with a history of type 2 diabetes mellitus and recently diagnosed metastatic ovarian cancer and now acute kidney injury (AKI).
NephronStop… let’s see what we can dissect from that.
HenleYou will be all over this!
NephronNot another onconephrology case, Henle; let’s do some basic nephrology.
HenleHmmm. Actually, it really isn’t. She hasn’t yet received any chemotherapy or immunotherapy. Not even radiation. She was in the process of starting but hasn’t yet. Her serum creatinine is 7 mg/dL, and her BUN is 110 mg/dL.
Nephron(with awe): What?
HenleYes, and her serum creatinine was 0.7 mg/dL 1 year ago and 1.2 mg/dL 6 months ago, and just 1.3 mg/dL 2 weeks ago.
Nephron(angry): What?
Henle(surprised): There you go again—you are stealing my thunder. Yes, and a Foley catheter was placed, but with no urine output.
NephronIs there any hematuria?
Henle(rolling his eyes): Not really; she is not making any urine, so we can’t assess for proteinuria or hematuria.
NephronI am sure they did serologies before they called you.
HenleYes, so far: antinuclear antibody (ANA), C3, C4, ANCA, double-stranded DNA, and anti–glomerular basement membrane all are negative. She has a negative serum immunofixation, and her serum free light chain ratio was 2.
NephronStop right there. Before we go any further, let me summarize this. You have an older lady with recently diagnosed ovarian cancer with a rapidly rising serum creatinine.
Henle(wondering to himself about quick decision by Nephron): Yes; correct. By the way, she is not on any medications. No herbal agents, no proton pump inhibitors or nonsteroidal anti-inflammatory drugs—and her complete blood count is normal, making your favorite diagnosis of thrombotic microangiopathy less likely.
NephronOh! Oh! No! This is a good one! Glad you brought this one to me. Anuric kidney failure has very few causes. The top three are usually hydronephrosis, hydronephrosis, and hydronephrosis!
Henle(trying to remember): Haha… perhaps not. The renal sonogram—sorry, kidney sonogram—was negative for hydronephrosis.
Nephron(jumping in): Really….
HenleHmmm. You are too much! Stop interrupting. I even did a CT scan to see if there was something I was missing. There is significant retroperitoneal metastatic disease, and it seems worse than the prior scan 1 month ago.
Nephron(shocked): This is impressive! What are her electrolytes?
HenleSerum sodium is low at 125 mmol/L, and serum potassium is high at 5.8 mmol/L. And she has acidemia, with CO2 at 18 mm Hg.
NephronOf course, they are…
Henle(not sure): This is probably acute tubular injury or acute interstitial nephritis. What else could this be?
NephronHmmm. From what? Was there any hypotension, new medications…contrast material…any other insults?
Henle(confused): No to all.
Nephron(interrupting): Is there anything on her physical examination?
HenleSome abdominal distention, and 1+ edema in her lower extremities.
Nephron(confident): This is hydronephrosis.
HenleNo, the sonogram and CT scan were negative for hydronephrosis.
NephronSmells like a hydronephrosis to me. This is hydronephrosis.
Henle(puzzled): OK… but how can you have hydronephrosis without imaging findings?
NephronThe sonogram reads no hydronephrosis and/or dilation. But clinically, the only thing that makes sense to me is obstruction. Especially with the electrolyte findings and this sudden rise of serum creatinine in the setting of a retroperitoneal mass. Nondilated obstruction is not uncommon, especially in patients with cancer that affects the retroperitoneal regions. There is so much disease that there is no room for the kidney to expand. But that does not mean that hydronephrosis is not present. The syndrome of nondilated obstructive uropathy and AKI is well reported in that setting, although the literature suggests that this syndrome is rare, accounting for fewer than 5% of cases of urinary obstruction.
Henle’s eyes respond with shock.
HenleReally? You must be kidding!
NephronOne of the earlier studies looked at a series of patients at a single center and found that the most common cause of nondilated hydronephrosis was cancer (likely related to retroperitoneal disease): prostate, colon, bladder, cervical, ovarian, lymphomas. Antegrade urography can help. The first-ever case of this was described in 1948 in someone with retroperitoneal fibrosis.
Henle, puzzled, leaves the room but returns in 2 days.
NephronAnd?
Henle(with a smile): We asked radiology to place percutaneous nephrostomy tubes, and there was significant bilateral obstruction. The patient’s serum creatinine is improving. Her electrolytes have improved as well.
Nephron(jumping in): Despite the absence of dilation on renal imaging, a strong suspicion for nondilated obstructive uropathy led to decompression procedures with prompt recovery of kidney function in your patient. This has been reported in the radiology literature. It is an important differential diagnosis to consider. Treatment is usually diagnostic. Given the pathologic features, the ureteral stents sometimes get restenosed and are unable to adequately decompress the collecting system. Percutaneous nephrostomy is usually the best procedure in such situations. Educating our urology and radiology colleagues about this entity is extremely important.
Henle(surprised): This is just fascinating and so refreshing. I love nephrology.
NephronHyponatremia and hyperkalemia have been reported with hydronephrosis as a result of the effect on the Na+-2Cl-K+ channels and Na+-K+ATPase pump being downregulated. The AKI itself can be responsible for these rapid electrolyte disorders from the hydronephrosis.
NephronWell done, apprentice. Keep an open mind. Again, never assume. Anuric AKI has very few causes: hydronephrosis, hydronephrosis, and then perhaps acute tubular injury, acute interstitial nephritis, and then cortical necrosis. Again, a quick diagnosis here and a therapeutic procedure saved this patient’s kidneys!
Henle(laughing): I need some coffee—the super New York style.

Detective Nephron was developed by Kenar D. Jhaveri, MD, professor of medicine at Donald and Barbara Zucker School of Medicine at Hofstra/Northwell. Thanks to Rimda Wanchoo, MD, associate professor of medicine at Zucker School of Medicine at Hofstra/Northwell, for her editorial assistance. Send correspondence regarding this section to kjhaveri@northwell.edu or kdj200@gmail.com

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