What is the next step in managing a 26-week pregnant female with recurrent right flank pain and hydronephrosis?

Management of Symptomatic Hydronephrosis in a 26-Week Pregnant Female

Ultrasonography with color Doppler of the kidneys and bladder is the first-line diagnostic approach for a 26-week pregnant female with recurrent right flank pain and hydronephrosis.

Initial Diagnostic Approach

• Ultrasonography is the imaging tool of choice in pregnant patients with flank pain due to its reasonably good sensitivity for stone detection without exposing the mother or fetus to ionizing radiation (rating of 8, or usually appropriate) 1
• Color Doppler ultrasonography allows for measurement of renal resistive indices (RI), which can help distinguish between physiologic pregnancy-related hydronephrosis and pathologic obstruction 1
• An RI elevation over 0.70 suggests underlying kidney dysfunction, and an RI difference of 0.04 between normal and abnormal kidneys is consistent with pathologic urinary tract obstruction 1
• Evaluation of ureteral jets with color Doppler can further help distinguish between obstructive and non-obstructive hydronephrosis 1

Differential Considerations

• Physiologic hydronephrosis occurs in 70-90% of pregnant women, typically more pronounced on the right side, due to mechanical compression from the enlarged uterus and progesterone-induced smooth muscle relaxation 1
• Symptomatic hydronephrosis affects approximately 0.2-4.7% of pregnant women, with higher prevalence in advancing trimesters and multiparous patients 1
• Urolithiasis complicates up to 0.8% of pregnancies and is a common cause of symptomatic hydronephrosis 2
• Untreated symptomatic hydronephrosis may lead to preterm labor or maternal/fetal death 1, 2

Management Algorithm

Step 1: Initial Conservative Management

• Begin with conservative measures including analgesics, hydration, and positional changes 3, 4
• Placing the patient on the side opposite to the affected kidney or in the knee-elbow position can reduce the extent of hydronephrosis 5, 4
• Repeat ultrasonography after positional changes (dynamic ultrasonography) to differentiate pregnancy-related hydronephrosis from pathologic causes 4

Step 2: Determine Need for Intervention

Indications for intervention include:

• Persistent pain despite conservative treatment 3
• Progressive hydronephrosis (>2 cm dilatation of the renal pelvis) 3
• Presence of uterine contractions 3
• Evidence of infection (pyonephrosis requires immediate treatment) 6

Step 3: Interventional Management

If intervention is required:

• Ureteral stent placement under ultrasound guidance is the preferred approach for decompression 3
• Percutaneous nephrostomy (PCN) is an alternative when ureteral catheterization is not technically possible 1
• The incidence of spontaneous abortion or preterm labor related to PCN tube placement is exceedingly low 1

Important Considerations

• MRI can be considered if ultrasonography is inconclusive, as it is highly dependable in depicting hydronephrosis and perinephric edema 1
• Low-dose non-contrast CT should be reserved for problematic situations when diagnosis cannot be made with ultrasonography or MRI 1
• If stones are suspected and conservative management is ineffective or surgery is expected, non-contrast CT may be recommended 1
• Nephrostomy catheters are typically left in place until after delivery, with definitive stone intervention performed postpartum 1

Pitfalls to Avoid

• Do not assume all hydronephrosis in pregnancy is physiologic; symptomatic hydronephrosis requires careful evaluation 6, 2
• Avoid unnecessary radiation exposure; use ultrasonography as the first-line imaging modality 1
• Don't delay treatment of pyonephrosis or cases with evidence of obstruction with high intra-renal pressure, as this can lead to kidney dysfunction 6
• Remember that the clinical significance of hydronephrosis lies in the association between ureteral obstruction and the high frequency of ascending urinary tract infection during pregnancy 5