When the Kidneys Pause: A Case of Reflex Anuria

Introduction: Anuric acute kidney injury (AKI) is defined as sudden cessation of urine output. Here, we report a case of reflex anuria (RA). Case Description: A 77-year-woman with recurrent diverticulitis was admitted for extensive sigmoid diverticulitis and posterior abscess resection. Bilateral ureteral stents were placed prior to surgery. At the end, both stents were removed, and a foley was placed. The patient was non-oliguric on POD 1 and 2 but became anuric on POD 3 with a creatinine of 2.3 mg/dL, from her baseline of 0.5 mg/dL. After a trial of 1L isotonic fluid and then 40mg IV furosemide, she remained anuric. Ultrasound revealed mild hydronephrosis of the left kidney and a normal right kidney/bladder. On POD 5, retrograde pyelogram (RP) revealed bilateral hydroureteronephrosis. Ureteral stents were placed with brisk urine output. In the upcoming days, creatinine returned to baseline. Discussion: In this case, RA was the leading diagnosis. There have been few reports that describe RA as a cause of AKI post urinary tract manipulation. One of the earliest descriptions is “cessation of urine output from both kidneys in response to irritation or trauma to one kidney or its ureter” (Hull et al., 1980). The exact pathophysiology is unknown, but there are two proposed mechanisms: 1. Neurovascular reflex: stimuli on the kidney’s afferent nerves result in intrarenal vasoconstriction 2. Ureterorenal reflex: stimuli affecting the ureter cause ureteral spasm with involuntary contraction of the smooth muscle. In this case, it is likely the mechanical manipulation from the stents that resulted in the ureteral spasm. This can lead to temporary blockage of the ureter and a “functional” obstruction from a physiological response. Reports have indicated that conservative management can result in self-resolution, however ureteral stenting is indicated in severe cases. In this case, there was a large discrepancy between US findings of mild, unilateral hydronephrosis and RP findings of severe bilateral obstruction, demonstrating that additional imaging may be required when there is a high index of suspicion. One proposed method to reduce the risk of RA with prophylactic stent placement is to use staged removal of both stents over 24 hours. In summary, reflex anuria is a diagnosis of exclusion and should be on the differential for a patient with sudden cessation of urine output, particularly after manipulation of the ureteral tract.