Renal Profile and Outcome of Patients With Post-Obstructive Diuresis at the UST Hospital: A Retrospective Study

Background of the Study: Post-obstructive diuresis (POD) is a common diagnosis among urologic patients that is medically diagnosed and managed. It is defined as urine production exceeding 200 mL per hour for two consecutive hours or producing greater than 3 L of urine in 24 hours. There is limited data on the risk factors of developing POD, but the need to identify such is important to prevent its complications such as dehydration, electrolyte imbalance, acute renal failure and even death. Objectives: The study aims to identify clinical and renal predictors of developing POD. It also seeks to show the outcome of patients diagnosed with POD and its correlation with medical management. Method: This is a retrospective study of all patients diagnosed with POD centered in the University of Santo Tomas Hospital from January 2017 to December 2018. Renal parameters such as serum creatinine, sodium, potassium, urea and ionized calcium were analyzed. Urinalysis and arterial blood gases were also noted and correlated. Results: Among a total of 106 patients with obstruction, 28.32% developed POD after decompression. The mean age is 58.2 ± 13.89, and most are male. Patients with POD have significantly longer days of obstruction (14 days, p = 0.049) compared to non-POD. Overweight patients comprise a significantly larger proportion of patients who had POD (p = <0.001). Those with baseline acute kidney injury (AKI) (elevated serum creatinine at an average of 1.93 and low eGFR at an average of 35.6) have a significantly higher risk of developing POD (p = 0.004). Serum sodium levels were also higher among patients with POD (140, p = 0.008). Renal predictors identified include obstruction from prostate cancer (p = 0.011), longer duration of obstruction (p = 0.042), low eGFR (p = 0.009) and AKI (p = 0.004). Intravenous fluid (IVF) did not differ in the type used and outcomes of POD. Fluid replacement per urine volume also did not alter the disease course (p = 801). Regarding outcome, all discharged patients improved but differed significantly from the non-POD group regarding prolonged hospital stay. There were no significant electrolyte imbalances, postoperatively. Conclusion: POD occurs more likely among patients with a baseline AKI, low level of eGFR, longer duration of obstructions beyond 14 days and those with prostate cancer. Serum sodium and creatinine were higher among patients with POD. POD is associated with prolonged hospital stay, but obstruction relief leads to renal function improvement.