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Postobstructive diuresis and its biochemical characteristics in children undergoing pyeloplasty for unilateral
Ashitosh D Pokharkar1, Rohit Bhashkar Meshram1, Charu Yadav1
1Department of Pediatric Surgery, Lady Hardinge Medical College & Kalawati Saran Children's Hospital, New Delhi, 110001, India.
Insights
Postobstructive diuresis (POD) in pediatric patients after pyeloplasty for unilateral pelviureteric junction obstruction (PUJO) shows biochemical similarities to animal models. Larger, hydronehydrotic kidneys with thinner parenchyma are more prone to POD and potential electrolyte imbalances.
Area of Science:
- Pediatric Urology
- Nephrology
- Surgical Outcomes
Background:
- Limited data exists on postobstructive diuresis (POD) in pediatric patients following pyeloplasty for unilateral pelviureteric junction obstruction (PUJO).
- Animal studies on POD characteristics are not well-translated to human pediatric cases.
Purpose of the Study:
- To assess biochemical characteristics of POD from the operated kidney.
- To evaluate clinical implications and identify predisposing factors for POD.
Main Methods:
- Prospective observational study of pediatric patients undergoing pyeloplasty for unilateral PUJO.
- Comparison of post-operative differential urine output (UO) between operated (OK) and contralateral kidneys (NCK).
- Categorization into groups with and without POD, analyzing urine biochemistry and electrolyte derangements.
Main Results:
- POD occurred in 60.4% of patients within 48 hours post-surgery.
- Patients with POD had significantly lower renal parenchymal thickness and higher renal pelvis antero-posterior diameter (APD), indicative of severe hydronephrosis.
- Urine biochemistry largely matched animal studies, except for higher FeK+ excretion; four patients required nephrology consultation for electrolyte derangement.
Conclusions:
- High UO from the operated kidney is the primary contributor to POD.
- Larger, hydronephrotic kidneys with parenchymal thinning are predisposed to POD.
- Subclinical injury to the contralateral kidney can limit compensation, leading to electrolyte derangements and necessitating close monitoring.
Background:
The characteristics of postobstructive diuresis (POD) following relief of unilateral ureteric obstruction (UUO) has been studied in animals, but there is scarcity of literature on translation of these findings in human pediatric patients with unilateral pelviureteric junction obstruction (PUJO) following pyeloplasty.
Objective:
The primary objective was to assess the biochemical characteristics of the POD from the operated kidney. Our secondary objective was it's clinical implications and identifying predisposing factors.
Study Design:
A prospective observational study was conducted on pediatric patients who underwent pyeloplasty for unilateral PUJO. Post-operative differential urine output (UO) from the operated kidney (OK) was compared with the normal contralateral kidney (NCK). Patients were divided into two groups: Group-1 with POD [n = 32; 60.4%] and Group-2 without POD [n = 21; 39.6%]. Data was collected for the occurrence of POD, urine biochemistry and postoperative electrolyte derangement requiring nephrology consultation.
Results:
POD occurred in Group-1 patients within 48-h after surgery. They had statistically significant lower median renal parenchymal thickness and higher median renal pelvis antero-posterior diameter (APD), differential ratio of kidney size and proportion of grade-4 hydronephrosis (HN) than Group-2 patients. None of the kidneys with PUJO were small in size. The abnormal biochemistry of POD from OK matched with experimental animal studies except the FeK+ excretion which was significantly higher [13,14,15]. Four patients in Group-1 required nephrology consultation for prolonged POD with electrolyte derangement: one concomitant pyelonephritis in NCK and other three with past history of renal injury. Predisposing factors for POD were parenchymal thinning in enlarged kidneys with SFU grade-4 hydronephrosis and higher renal pelvis APD.
Discussion:
Urine biochemistry in human pediatric subjects matches animal studies to a large extent except FeK + excretion and suggests compensation by NCK to maintain homeostasis during POD. Besides the predisposing factors in OK, concomitant or pre-existing (subclinical) functional injury to NCK despite normal appearance on preoperative imaging may limit the compensation resulting in electrolyte derangement.
Conclusions:
High UO from OK mainly contributes to POD. Larger hydronephrotic kidneys with parenchymal thinning are more predisposed to POD. Our observations reveal that concomitant or prior subclinical injury to NCK may not be apparent on preoperative imaging and it could be a warning signal to the clinician for occurrence of electrolyte derangement with prolongation of POD and such patients should be monitored closely during post-operative period.
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