Can patients pass a kidney stone through a stoma (stomal opening)?

Can Patients Pass Kidney Stones Through a Stoma?

Yes, patients with urinary diversion stomas (such as ileal conduits) can pass kidney stones through the stoma, though the stones often require endoscopic intervention rather than spontaneous passage due to altered anatomy.

Understanding Stone Passage in Patients with Urinary Stomas

Spontaneous Passage Considerations

In patients with ileal conduit urinary diversions, kidney stones can theoretically pass through the stoma opening, but several anatomical factors make this less predictable than in patients with intact urinary tracts:

• Stone size remains the primary determinant: Stones ≤5 mm have approximately a 68% chance of spontaneous passage in normal anatomy, while stones 5-10 mm have only a 47% passage rate 1, 2
• The ileal conduit itself can develop stenosis over time, which may impede stone passage and cause upper urinary tract damage 3
• Ureteral-ileal anastomotic strictures are common complications that can prevent stones from reaching the conduit and exiting through the stoma 3

Preferred Management Approach

A retrograde approach through the stoma should be considered first-line therapy for treating renal stones in patients with ileal conduits, as it offers lower morbidity than percutaneous access 4:

• Retrograde ureteroscopy via the stoma allows direct visualization and stone extraction with stone-free rates of approximately 90-95% for stones requiring intervention 5, 4
• This approach avoids the complications associated with percutaneous nephrostomy, particularly in patients with bone deformities or lack of ureteral reflux from the reservoir 4
• An antegrade or combined approach may be necessary if the retrograde approach fails, particularly if there is significant conduit stenosis 4

Medical Expulsive Therapy Limitations

While alpha-blockers increase stone passage rates by 29% in patients with normal anatomy 5, 1, their efficacy in patients with ileal conduits is uncertain:

• The altered anatomy and potential for conduit stenosis may limit the effectiveness of medical expulsive therapy 3
• Conservative management should be limited to 4-6 weeks maximum to avoid irreversible kidney injury 6, 2

When to Intervene

Intervention is warranted under the following circumstances:

• Uncontrolled pain despite adequate analgesia 6
• Signs of infection or sepsis, which require urgent decompression 5
• Development of obstruction or hydronephrosis 6
• Failure of spontaneous passage after 4-6 weeks 6, 2

Common Pitfalls

• Do not assume normal spontaneous passage rates apply to patients with urinary diversions, as conduit stenosis and anastomotic strictures are common long-term complications 3
• Avoid prolonged observation beyond 6 weeks, as patients with ileal conduits are at higher risk for upper tract deterioration 3
• Be aware that patients with ileal conduits have increased risk of uric acid stones due to bicarbonate loss in the conduit effluent, leading to acidic urine 7
• Consider that bone deformities may make percutaneous access challenging, making the retrograde approach through the stoma more practical 4

Long-term Monitoring

Patients with urinary stomas require stringent follow-up:

• Regular imaging to assess for conduit stenosis and upper tract changes 3
• Monitoring for recurrent stone formation, as these patients often have metabolic abnormalities including low urine volume, hypocitraturia, and acidic urine 7
• Evaluation by stoma care specialists to ensure proper stoma function and prevent complications 3