Hello everyone, today let's discuss a common issue many patients experience after anal surgery—even when there's little stool, they constantly feel the urge to defecate. What exactly causes this strong sensation? Let's explain it in plain language based on medical principles.

1. The wound becomes "inflamed and irritable," making the nerves hypersensitive.

The skin and mucous membranes around the anus are densely populated with sensory nerve endings (primarily innervated by the pudendal nerve), which act like "human alarm systems" and are naturally sensitive to various stimuli. Surgery is akin to "accidentally making a cut in this area," and during wound healing, edema and inflammation occur, prompting the body to release inflammatory factors such as prostaglandins and bradykinin. This essentially "turns up the sensitivity dial" on the nerve alarm system. For example, under normal circumstances, slight pressure changes during intestinal peristalsis (e.g., rectal pressure reaching 50mmHg) might simply register as a mild sensation. However, post-surgery, inflamed tissues cause the nerves to become overly reactive. Even at pressures as low as 20mmHg (like a balloon just beginning to inflate), the

nerves will urgently signal, "Need to defecate!" This phenomenon is medically termed "peripheral sensitization."

2. The anal "sphincter muscles" remain tense, constantly sending false signals.

The anal area is surrounded by crucial sphincter muscles, which act like "valves" controlling bowel movements, consisting of both internal and external sphincters. After surgery, the body’s protective response causes these muscles to "involuntarily tighten" (similar to instinctively pulling your hand back when burned), leading to protective spasms. This results in a lower "pressure threshold" for the valve. Normally, the rectum accumulates stool until a certain volume (e.g., internal pressure reaches 70 mmHg) before triggering the defecation reflex. However, post-surgery, the overly tense valve may misinterpret even small amounts of stool or gas (internal pressure as low as 30 mmHg), falsely signaling to the brain that "it’s time to open"—clinically termed as hyperactive pseudo-defecation reflex.

3. Psychological Stress Fuels the Problem, Creating a "Sensitivity Loop"

Postoperative anxiety isn’t just "overthinking"—it activates the body’s HPA axis (hypothalamic-pituitary-adrenal axis), increasing levels of the "stress hormone" cortisol. This hormone heightens the sensitivity of intestinal and anal nerves, much like how some people experience "cramping and diarrhea" when stressed. Worse, this sensitivity can create a "vicious cycle": the more you focus on anal sensations, the stronger the urge to defecate; the stronger the urge, the greater the stress, which further amplifies nerve sensitivity. Over time, spinal nerve cells may even "memorize" this overreaction, leading to central sensitization—making the sensation of needing to defecate increasingly persistent.​

Scientific Response: Targeting Three Key Areas for "Systematic Breakthrough"

Calming those sensitive nerves: Doctors may prescribe anti-inflammatory suppositories like diclofenac sodium, which reduce prostaglandin synthesis to "cool down" irritated nerves and lower their excitability;

Relax tense anal muscles: Biofeedback therapy (similar to performing "anal muscle exercises" with equipment) can be done to learn voluntary relaxation of sphincter muscles by monitoring electromyographic signals, helping restore normal pressure thresholds for bowel movements

Breaking the vicious cycle between psychology and nerves: Try relaxation methods such as mindful breathing and meditation to reduce stress hormone levels and prevent the worsening of the "psychological tension → nerve sensitivity" cycle. Clinical studies show that standardized intervention can shorten the duration of frequent bowel urges by 40%–60%.

Please note: If the sensation of incomplete bowel movement is accompanied by severe pain, bloody stools, or persistent tightness in the anus, you must inform your doctor promptly to rule out issues such as wound infection or scar contracture.

To summarize, the strong urge to defecate after surgery results from a combination of wound inflammation stimulation, muscle spasms, and psychological stress—much like the body is "overprotecting" the injured anus. This phenomenon gradually diminishes as the wound heals and with proper postoperative care. Understanding these mechanisms not only helps us recognize the body’s response but also boosts confidence in following treatment. We hope today’s explanation has been helpful—thank you!