Why does a patient experience urinary retention after a hemorrhoidectomy?

Why Urinary Retention Occurs After Hemorrhoidectomy

Urinary retention is a common complication after hemorrhoidectomy, occurring in 2-36% of patients, with multiple contributing mechanisms including reflex bladder dysfunction from anal pain and sphincter spasm, neurogenic factors from anesthesia, and local pelvic floor trauma. 1

Primary Mechanisms

Pain-Mediated Reflex Inhibition

• Severe postoperative anal pain triggers reflex inhibition of the detrusor muscle through sacral nerve pathways, preventing normal bladder contraction. 2, 3 This is the most common mechanism, as narcotic analgesics are generally required after hemorrhoidectomy and most patients experience significant pain for 2-4 weeks. 1

• Excruciating anal pain at the surgical site creates a vicious cycle where patients avoid voiding due to fear of pain, leading to bladder overdistension and subsequent inability to void. 3

• The anal sphincter spasm that accompanies postoperative pain contributes to pelvic floor muscle dysfunction, further impairing normal micturition reflexes. 2

Anesthesia-Related Factors

• Spinal and epidural anesthesia significantly increase urinary retention risk compared to general anesthesia. 4, 2 Logistic regression analysis showed epidural anesthesia (p=0.008, OR not specified) and spinal anesthesia (p=0.016) were independent predictors of postoperative urinary retention. 2

• General anesthesia was associated with a lower incidence of urinary retention (p=0.044; OR 2.43; 95% CI 1.02-5.97), meaning patients under general anesthesia had 2.43 times lower odds of developing retention compared to regional anesthesia. 4

• Regional anesthesia causes temporary autonomic dysfunction affecting bladder innervation, with effects potentially lasting 24-48 hours postoperatively. 2

Surgical Technique and Severity

• More extensive hemorrhoid disease (third- and fourth-degree hemorrhoids) significantly increases retention risk. 2 Hemorrhoids with severity of three degrees or higher were independent predictors of urinary retention (p=0.017). 2

• Conventional hemorrhoidectomy (Milligan-Morgan or Ferguson techniques) has higher retention rates (21% in one study) compared to stapled hemorrhoidectomy (7.8%, p=0.009). 4 Stapled hemorrhoidectomy was an independent protective factor (p=0.046; OR 2.66; 95% CI 1.02-7.00). 4

• The use of excessive retraction with extensive dilation of the anal canal during surgery causes sphincter injury and contributes to postoperative voiding dysfunction. 1

Bladder Overdistension

• Intraoperative and immediate postoperative fluid administration without adequate bladder drainage leads to overdistension, which damages detrusor muscle contractility and impairs subsequent voiding ability. 5

• Subclinical obstructive bladder dysfunction present preoperatively becomes clinically apparent after surgery when combined with other risk factors. 5

Patient-Specific Risk Factors

Demographics and Comorbidities

• Male sex is a major risk factor, with 4.7% of males developing retention compared to 2.9% of females after general surgical procedures. 5

• Advanced age increases retention risk, with frequency increasing progressively with each decade. 5

• Abnormal voiding history was present in 80% of patients who developed postoperative retention, indicating pre-existing bladder dysfunction. 5

Medication Effects

• Sympathomimetic and anticholinergic medications administered during or after anesthesia contribute to retention by affecting bladder contractility and sphincter tone. 5

• Parasympathomimetics have been used to avoid urinary retention, though results have been limited or mixed. 1

Postoperative Mobility

• Inability to stand or sit after surgery significantly increases retention risk by preventing normal voiding posture and increasing pelvic floor tension. 5

Clinical Presentation and Complications

Warning Signs

• The clinical triad of severe pain, high fever, and urinary retention suggests necrotizing pelvic sepsis, a rare but life-threatening complication requiring emergency examination under anesthesia with radical debridement. 1

• Risk of necrotizing infection is increased in immunocompromised patients, including those with uncontrolled AIDS, neutropenia, and severe diabetes mellitus. 1

Severe Complications

• Long-lasting urinary retention can progress to renal failure if not recognized and treated appropriately. 3

• An unhealed anal wound, inappropriate low-fiber diet, and excruciating anal pain represent key factors initiating the sequence ending in urinary retention. 3

Prevention Strategies

Anesthesia Selection

• General anesthesia should be strongly considered over spinal or epidural anesthesia to reduce retention risk. 4, 2

Surgical Technique

• Stapled hemorrhoidectomy reduces retention incidence compared to conventional techniques due to less postoperative pain. 4

• Limiting incision size and avoiding excessive anal canal dilation minimizes sphincter trauma. 1

Perioperative Management

• Patients with abnormal voiding history should undergo preoperative urological evaluation, and infravesical obstruction should be relieved before elective hemorrhoidectomy. 5

• Prophylactic catheterization should be considered for high-risk patients (males, elderly, those with obstructive symptoms) undergoing hemorrhoidectomy. 5

• Avoiding bladder overdistension during and immediately after surgery through appropriate catheter use or timed voiding is critical. 5

Postoperative Care

• Early warm water sitz baths starting 6 hours after surgery significantly reduce postoperative pain (B=-0.81,95% CI: -1.44 to -0.18) but do not prevent urinary retention. 6

• Adequate pain control with appropriate analgesics reduces reflex bladder inhibition. 1

• Early mobilization allowing patients to stand or sit for voiding should be encouraged when medically appropriate. 5

Common Pitfalls

• Never assume urinary retention is benign—prolonged retention can cause permanent bladder dysfunction and renal complications. 3

• Do not attribute all postoperative voiding difficulty to "normal" surgical effects; evaluate for serious complications like pelvic sepsis in patients with fever and severe pain. 1

• Avoid regional anesthesia in patients with pre-existing voiding symptoms or high-risk features for retention. 4, 2

• Ensure adequate fiber intake and stool softeners postoperatively to prevent straining and anal pain that perpetuate the retention cycle. 3