Men's Health

Can an Enlarged Prostate Cause Constipation? The Two-Way Link Explained

By VitalFitnessHub Editorial Team — September 14, 2026

In a national health survey of American men, those reporting three or fewer bowel movements a week were about twice as likely to say they could not empty their bladder completely and twice as likely to hesitate before the stream started, compared with men with normal bowel habits. Hard stools alone raised the odds of getting up at night to urinate by three-quarters. Those numbers, from an analysis of the National Health and Nutrition Examination Survey published in the Journal of Urology, are the clearest evidence that the bowel and the bladder in men are not separate systems that happen to share a neighborhood. They push on each other, literally.

So can an enlarged prostate cause constipation? Occasionally, and only when it is very large or has caused the bladder to fill and stay full. Far more often the arrow runs the other way: constipation makes an enlarged prostate's symptoms noticeably worse. Both directions are fixable, and the fixes overlap.

The Anatomy: Why Two Inches Matter

The prostate sits directly in front of the rectum, separated by a thin wall of tissue. That is why a doctor can feel it through the rectal wall during a digital rectal exam. Above the prostate is the bladder; behind and around all of it is the pelvic floor, the sling of muscle that both organs rely on to work.

Three consequences follow from that arrangement:

A full rectum presses forward on the prostate, the bladder neck, and the urethra. A hard, retained stool mass sitting against the prostate narrows an already narrowed channel.
A very enlarged prostate, or a chronically overfull bladder, presses backward on the rectum. This is the less common direction, but a bladder holding half a liter of retained urine is a large object in a small space.
Straining to pass stool spikes pressure inside the abdomen and pelvis and, over years, weakens the pelvic floor that both organs depend on.

Direction One: Constipation Worsens Prostate Symptoms

This is the direction with the most evidence, and it is the one most men experience without connecting the two.

Mechanical compression. A loaded rectum sits against the prostatic urethra. Men with moderate BPH often notice that a bad week of constipation brings a worse week of hesitancy, weaker stream, and the sense of not finishing. The survey odds above, roughly double for incomplete emptying and hesitancy in constipated men, fit that mechanism.

Fecal impaction can stop urination altogether. Emergency medicine and urology textbooks list severe fecal impaction among the causes of acute urinary retention, particularly in older men, because the impacted mass can pinch the bladder neck or prostatic urethra shut. A rectal exam is standard in evaluating a man who suddenly cannot urinate for exactly this reason. It is uncommon, but it is a real emergency that starts in the bowel.

Retained urine breeds infection. Constipation and a lazy, overfull bladder both leave stagnant urine behind, and stagnant urine grows bacteria. Men who reported constipation in one series had close to three times the odds of a urinary tract infection history compared with men with normal stools.

Straining damages the pelvic floor. Years of bearing down against hard stools stretch and weaken the muscles that support the bladder neck. That contributes to post-void dribbling and urgency, symptoms most men blame entirely on the prostate.

Direction Two: When the Prostate Side Causes the Bowel Problem

An enlarged prostate can contribute to constipation in three ways, and the first is by far the most common.

BPH medications. Men whose enlarged prostate comes with urgency and frequency, the storage symptoms, are often prescribed an antimuscarinic drug such as solifenacin or oxybutynin alongside their alpha blocker. Antimuscarinics slow the bowel as a side effect. In the NEPTUNE studies of a combined solifenacin and tamsulosin tablet in more than 1,000 men, constipation was the second most common adverse event, at 5.2 percent, after dry mouth. If your constipation started when a new prostate medication did, that is the first thing to tell your doctor; newer alternatives such as beta-3 agonists (mirabegron, vibegron) are much less constipating.

A chronically full bladder. When obstruction leads to chronic retention, the bladder can hold several hundred milliliters at all times. That mass presses on the rectum and can make complete evacuation harder, adding a feeling of rectal fullness and incomplete bowel emptying.

A very large gland. Prostates above roughly 80 to 100 grams, several times normal size, can themselves intrude on the rectal wall. This is unusual, and men with glands that large usually have prominent urinary symptoms first.

Breaking the Cycle: What Actually Helps Both

Because the two problems feed each other, the useful interventions tend to improve both at once.

Fiber and fluid, in that order. Most men eat far less than the 30 grams of fiber a day that keeps stool soft and bulky. Oats, beans, lentils, fruit with skin, and vegetables do the job; add psyllium if food alone falls short. Fiber without water makes things worse, so drink through the day, tapering in the evening so the extra fluid does not turn into night-time bathroom trips.

Move. Physical activity speeds bowel transit, and a meta-analysis of 43,000 men found moderate to high activity was associated with a 25 percent lower risk of BPH and urinary symptoms. Walking briskly most days serves both ends.

Stop straining; change position. Feet on a low stool, leaning forward, knees above hips, straightens the anorectal angle and lets stool pass with less force. Never strain against a closed pelvic floor; if nothing comes in a few minutes, get up and try later.

Audit the medicine cabinet. Beyond antimuscarinics, common constipators include opioid painkillers, iron supplements, calcium supplements, some blood pressure drugs, and older antihistamines. The last group also worsens urinary retention, a double hit for men with BPH.

Treat the obstruction. Reducing the prostate's squeeze on the urethra reduces retained urine, which reduces both the infection risk and the backward pressure on the rectum. Weight loss, walking, and, when needed, alpha blockers or 5-alpha reductase inhibitors are covered in our guide to reducing an enlarged prostate without surgery. Note that 5-alpha reductase inhibitors and alpha blockers are not significantly constipating, so switching a storage-symptom drug for better obstruction treatment is often the answer when a man has both problems.

Supplements, kept in proportion. Saw palmetto failed its two largest trials. Beta-sitosterol, a plant sterol, improved symptom scores by about 4.9 points in a Cochrane review, without shrinking the gland. ProstaVive combines nettle root, boron, and Panax ginseng and is a reasonable non-prescription starting point for mild urinary symptoms alongside the changes above. It has no direct effect on bowel function, is not a substitute for medication, and comes with a 180-day money-back guarantee so you can judge it over a real timeframe.

Frequently Asked Questions

Can constipation cause urinary retention? Yes. Severe constipation or fecal impaction is a recognized cause of acute urinary retention in men, and milder constipation measurably worsens incomplete emptying and hesitancy.

Does an enlarged prostate affect bowel movements? Usually only indirectly, through medications or a chronically full bladder. A gland large enough to physically obstruct the rectum is rare.

Can straining to poop damage the prostate? It does not damage the prostate itself, but chronic straining weakens the pelvic floor and raises pelvic pressure, both of which worsen urinary symptoms and can contribute to hemorrhoids.

Is rectal pressure a sign of prostate problems? It can be, particularly with prostatitis, which causes perineal and rectal discomfort. With plain BPH, rectal pressure more often reflects constipation or a full bladder. Persistent rectal fullness with blood in the stool is a bowel symptom that needs its own evaluation, not a prostate explanation.

When to See a Doctor

Go promptly if you cannot urinate, if you have not passed stool in several days and have abdominal pain or vomiting, or if you see blood in either urine or stool. Book a routine visit if constipation began with a new prostate medication, if you need laxatives more than occasionally, or if bowel and bladder symptoms are both getting worse together. For men over 50 with new urinary symptoms, the standard exam and PSA discussion apply regardless. The complete picture of what prostate symptoms mean and how they are managed is in our prostate health guide for men over 50.

Looking for a non-prescription starting point for mild urinary symptoms? >> See what's in ProstaVive and how the 180-day guarantee works

Sources

Rohrmann S et al. Association of bowel habits with lower urinary tract symptoms in men: findings from NHANES 2005–2008. Journal of Urology, 2013. PubMed
NIDDK. Digestive diseases statistics for the United States (constipation prevalence). NIDDK
Male Urinary Retention: Acute and Chronic (fecal impaction as a cause). StatPearls, NCBI Bookshelf. NCBI
Urinary Retention in Adults: Evaluation and Initial Management. American Family Physician, 2018. AAFP
Drake MJ et al. Long-term safety and efficacy of single-tablet combinations of solifenacin and tamsulosin OCAS in men with storage and voiding LUTS (NEPTUNE / NEPTUNE II). European Urology, 2015. PubMed
Parsons JK, Kashefi C. Physical activity, benign prostatic hyperplasia, and lower urinary tract symptoms. European Urology, 2008. PubMed
Bent S et al. Saw palmetto for BPH (STEP). NEJM, 2006; Barry MJ et al. (CAMUS). JAMA, 2011. Summary
Wilt TJ et al. Beta-sitosterols for benign prostatic hyperplasia. Cochrane Database of Systematic Reviews, 1999. Cochrane