From the Guidelines
Differential urine output between bilateral nephrostomies is primarily caused by differences in kidney function, obstruction status, or technical factors related to the nephrostomy tubes themselves, with asymmetric kidney function being the most common cause. The most recent and highest quality study on this topic is from 2020, published in the Journal of the American College of Radiology 1. This study highlights the importance of understanding the causes of differential urine output in patients with bilateral nephrostomy tubes, as it can significantly impact patient management and outcomes.
Causes of Differential Urine Output
- Asymmetric kidney function, where one kidney has better filtration capacity than the other due to chronic disease, acute injury, or congenital differences
- Partial obstruction of one nephrostomy tube, which can occur from blood clots, debris, sediment, or tube kinking, reducing output from the affected side
- Positioning issues, such as improper tube placement or migration, can affect drainage efficiency
- Anatomical variations between kidneys, including size differences or collecting system anomalies, naturally lead to output discrepancies
- Infection affecting one kidney more severely than the other can temporarily reduce function on the infected side
Management
- Regular assessment of tube patency through gentle irrigation with sterile saline if clinically indicated
- Monitoring for signs of infection
- Ensuring proper tube positioning
- Investigating significant output differences with imaging studies like ultrasound or CT to identify underlying causes
- A recent study demonstrated the superiority of third-generation cephalosporin ceftazidime versus fluoroquinolone ciprofloxacin in both clinical and microbiological cure rates with improved early and long-term cure rates in those who received PCN versus ureteral stent 1
Clinical Implications
Understanding the causes of differential urine output in patients with bilateral nephrostomy tubes is crucial for clinicians to appropriately interpret output differences and determine when intervention is necessary versus when differences represent expected physiological variation. This knowledge can help guide management decisions, such as the need for tube irrigation, imaging studies, or antibiotic therapy, and ultimately improve patient outcomes. A study comparing double-J ureteral stent placement versus PCN demonstrated no significant difference between the two groups in regard to operative and imaging times, but the number of subsequent interventions was significantly higher in the PCN group 1.
From the Research
Causes of Differential Urine Output
- Differential urine output in patients with bilateral nephrostomy tubes can be caused by various factors, including obstruction, infection, and bleeding 2, 3, 4, 5.
- Obstruction can occur due to kinking, dislodgment, or migration of the nephrostomy tube, leading to decreased urine output 2.
- Infection can also cause differential urine output, as purulent urine was extracted in 10 cases in one study 3.
- Bleeding is another potential cause, as hematuria was common in 34 cases in one study 3.
Factors Affecting Urine Output
- The type and degree of obstruction can affect urine output, with unilateral obstruction being more common in one study 5.
- The presence of malignancy can also impact urine output, as malignant disease was the cause of obstruction in 70% of patients in one study 5.
- The glomerular filtration rate (GFR) can also be affected, with a significant decrease in serum creatinine and increase in GFR observed after percutaneous nephrostomy placement in one study 5.
Management and Complications
- Percutaneous nephrostomy is a safe and effective treatment option for urinary tract obstruction, especially in patients with malignancies 4, 5.
- Complications can include bleeding and infection, but these did not result in any fatalities in one study 5.
- Continuous monitoring is essential to assess long-term complications and the longevity of nephrostomy tube functionality 5.