Why is a urology (urinary) stent needed in patients with colon cancer?

Urinary Stents in Colon Cancer: Indications and Management

Urinary stents are primarily needed in colon cancer patients when the tumor causes extrinsic compression of the ureter, leading to hydronephrosis and potential renal dysfunction. This obstruction typically occurs when colon cancer invades or compresses the ureter, particularly in advanced or locally invasive disease 1.

Pathophysiology and Indications

Colon cancer can cause ureteral obstruction through several mechanisms:

• Direct tumor invasion into the ureter
• Extrinsic compression from primary tumor mass
• Retroperitoneal lymph node metastases causing compression
• Peri-ureteric fibrosis from previous radiation or chemotherapy 2

The consequences of untreated obstruction include:

• Progressive hydronephrosis
• Deteriorating renal function
• Risk of urinary tract infection and sepsis
• Electrolyte imbalances

Management Options

First-Line Approach: Retrograde Ureteral Stenting

Retrograde ureteral stenting is the first-line therapy for managing ureteral obstruction caused by malignancies 1. This involves:

• Cystoscopic placement of a double-J stent from bladder to kidney
• Advantages: Less invasive, avoids external drainage
• Technical success rate varies (25-75%) depending on degree of obstruction 3

Alternative: Percutaneous Nephrostomy (PCN)

PCN is indicated when:

• Retrograde stenting fails or is technically challenging
• Extrinsic compression is severe
• Obstruction involves the uretero-vesical junction
• Ureteral obstruction length exceeds 3 cm 1

PCN offers higher technical success rates in relieving obstruction compared to retrograde stenting in cases of extrinsic compression from malignancy 1.

Clinical Benefits and Outcomes

Proper urinary drainage through stenting or PCN provides:

1. Improved renal function in most cases 1
2. Potential survival benefits 1
3. Enhanced quality of life 1
4. Prevention of urinary sepsis and renal failure

However, the benefits must be weighed against potential complications:

• Risk of developing pyelonephritis or bacteriuria
• Neutropenia and history of UTI are significant risk factors for pyelonephritis 1
• Management of obstructive uropathy may increase risk of symptomatic bacteriuria 1

Patient Selection Considerations

The most appropriate candidates for urinary stenting are:

• Patients with reasonable treatment options for their malignancy 1
• Those with life expectancy of at least 6 months 4
• Patients with increasing serum creatinine levels 4
• Those experiencing severe clinical symptoms associated with hydronephrosis 4

For patients with advanced disease receiving only palliative care, PCN may offer limited benefit as:

• Patient performance status and survival rates are often poor
• Further procedures may be necessary 1
• The procedure itself carries significant morbidity 1

Stent Types and Duration

Standard Polymeric Stents

• Require regular exchange (typically every 3 months)
• Higher risk of encrustation and migration
• Limited success for long-term patency 2

Metallic Stents

• Provide longer functional duration (average 4 months longer than polymeric stents) 5
• Better option for long-term maintenance of ureteric patency
• Fewer hospital admissions for stent changes 2
• Should be considered after polymeric stent failure 5

Complications and Prevention

Common complications include:

• Infection (1-19% for PCNTs, 11% for ureteral stents) 1
• Encrustation
• Migration
• Hematuria
• Perforation (rare but serious) 6

Prevention strategies:

• Preprocedural antimicrobials for elective PCNT and ureteral stent placement 1
• Regular assessment of continued need for stents
• Maintaining clean exit site with antiseptic use
• Regular dressing exchange for PCNTs
• Avoiding concomitant use of Foley catheters when feasible 1

Conclusion

Urinary stents play a crucial role in managing ureteral obstruction caused by colon cancer, preserving renal function and improving quality of life. The choice between retrograde stenting and PCN should be based on technical feasibility, degree of obstruction, and patient factors. Regular monitoring and timely exchange of stents are essential to prevent complications and maintain effectiveness.