Nonobstructive Hydronephrosis Due to Social Polydipsia

A Case Report

Natallia Maroz; Uladzimir Maroz; Saima Iqbal; Ravi Aiyer; Ganesh Kambhampati; A A Ejaz

Disclosures

J Med Case Reports. 2012;6(376) 

In This Article

Discussion

NOH is an uncommon entity that occurs in the pediatric and adult populations, primarily in patients with central and nephrogenic diabetes insipidus, both sporadically and in familial clusters.[5] NOH has been reported in 67% of patients with nephrogenic diabetes insipidus[6] and is not uncommon in those with psychogenic polydipsia.[7] In mice, mutations in the vasopressin-neurophysin II gene have been associated with familial neurohypophyseal diabetes insipidus,[8] and the S256L mutation in aquaporin-2 has been associated with congenital progressive hydronephrosis.[9] Our patient's condition differs from that in other published reports in that the NOH was not caused by psychogenic polydipsia, diabetes insipidus, obstruction, or genetic abnormalities, but was a sequela of an exaggerated social habit.

The lack of electrolyte abnormalities in our patient was remarkable. In fact, the ability to maintain a stable serum sodium level and concentrate urine with water deprivation along with bilateral hydronephrosis-hydroureter in the absence of an obstruction is diagnostic for NOH. The long-term consequences of NOH are not known, with reports of partial or complete resolution of hydronephrosis in the majority of reports. Several cases of familial nephrogenic diabetes insipidus were followed over periods of decades with observation of NOH, but no harmful impact on renal function was observed. A few cases have been described of reversible renal impairment in patients with NOH due to bladder overdistension and delayed voiding.[10,11] Rupture of the urinary tract and progression to end-stage kidney disease were also reported.[12,13] It is important to be cognizant of the latest outcome data from acute kidney injury research, which demonstrates a high risk of developing chronic kidney disease and the need for renal replacement therapy in patients with even mild increments in serum creatinine.[14]

The average capacity of the urinary system in a nonobstructive state for urine volume in an adult patient is 600mL to 1000mL with a bladder capacity of 400ml to 800mL. The average healthy adult perceives the need to void with a bladder filled to 50% of its capacity. Employed individuals frequently restrict their use of the bathroom during working hours, thereby promoting dilation of the urinary system. NOH represents benign fullness in the urine excretory system as a result of a mismatch of its capacity with respect to the excessive production of urine. The persistently large urine volumes in NOH lead to urinary bladder distension and hypertrophy, with subsequent intramural obstruction of the distal ureters. In time, bladder contractility is compromised, ureteric peristalsis diminishes, and large residual urine volumes worsen this functionally obstructive uropathy. Other studies have reported that normal detrusor contractility is maintained in NOH even with a large postvoidal urine residue and the dilation of the bilateral renal pelvis, ureter and bladder.[15]

NOH is a well-recognized entity during pregnancy and can be seen in up to 80% of pregnant women, with more prominent occurrence on the right side. The renal pelvis and calyces become dilated in pregnancy as a result of progesterone effects. It is important to emphasize that hydronephrosis caused by obstruction is much more common than NOH and frequently presents with flank pain and worsening of renal function. Although our patient had mild flank pain at presentation, her urological work-up results did not reveal the presence of ureteropelvic junction obstruction or vesicoureteral reflux, which would be suggestive of anatomical abnormalities. Patients with polydipsia can potentially develop a variant of a functional ureteropelvic junction obstruction because of the massive volume of urine exceeding the drainage capacity of the renal pelvis. It is important to recognize the presence of bilateral hydronephrosis and hydroureter (primarily in the upper and middle segments) in cases of NOH.

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