Constipation & UTI: What is the Link?

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1. Does constipation cause UTI in adults?

Constipation is a recognized risk factor for UTI, especially in children and adolescents. Although it is not a direct cause, constipation may play a role in predisposing to UTIs.

Severe cases of constipation may predispose to UTI through several factors. The sigmoid colon filled with stool in severe constipation may cause bladder dysfunction.

For example, one study found that patients with a history of UTIs are more likely to have constipation. Furthermore, the risk of UTI is higher with more severe forms of constipation (more feces in the recto-sigmoid area of the colon).

Another study (screenshot below) concluded that treating constipation is very important for treating some cases of UTIs.

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Correlation doesn’t always mean causation:

Although constipation is linked to urinary tract infection (correlation), this doesn’t always mean constipation is a cause or risk factor for UTIs.

Studies revealed anatomically, the anorectal area and the lower urinary tract are closely related.

Scientists proposed that your brain treats the anal and the urethral sphincter as a single functional unit.

Abnormal contractions of the anal and urethral sphincters may cause constipation and urinary stasis (which predispose to UTI).

So, the theory is that both constipation and UTI occur secondary to a common cause (sphincter dysfunction) rather than one causing the other.

This correlation between bladder dysfunction and constipation is often referred to as (reference):

  • Bowel and Bladder dysfunction (BBD)
  • Dysfunctional Elimination Syndrome (DES).

2. Causes of UTI in patients with constipation (theories):

Researchers have proposed several mechanisms by which constipation causes bladder dysfunction and UTIs (especially in children and adolescents):

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A. Theory 1: Pressure on the posterior bladder wall (by the distended rectum)

In severe constipation, the rectum (which lies just behind the urinary bladder) is often distended with stool.

As a result, direct pressure on the posterior bladder wall leads to overactivity of the main urinary bladder muscles (detrusor muscle), which leads to impaired bladder emptying and subsequent urinary tract infection (reference).

B. Theory 2: dysregulated bladder wall/urethral sphincter contraction.

Urination occurs through two main steps:

  • Contraction of the urinary bladder wall to expel the urine (detrusor muscle contraction).
  • Relaxation of the sphincters closing the urethra (the internal and external urethral sphincters).

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IMAGE SOURCE

Researchers proposed that your brain treats the anal and the urethral sphincter as a single functional unit.

So, prolonged contraction of the anal sphincter leads to concomitant prolonged contraction of the urethral sphincter of the bladder.

As a result, when the urination process starts, the bladder wall (detrusor muscle) contracts while the urethral sphincter fails to relax, leading to dysregulated urination, urine stasis, and UTI.

C. Theory 3: Pelvic floor muscle dysfunction.

Large amounts of stool lead to strong external anal sphincter relaxation (a part of the pelvic floor).

As a result, the whole pelvic floor contracts to support the external anal sphincter leading to failure of the relaxation of the urethral sphincter.

D. Theory 4: combined ureteric reflux, bowel, and bladder dysfunction.

BBD (bladder and bowel dysfunction) leads to upward urine reflux from the urinary bladder to the ureters and the kidney (a condition called ureteric or vesicoureteric reflux) (reference).

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VUR (vesicoureteric reflux) is a major risk factor for UTIs.

3. What is the link between UTI, constipation, and pregnancy?

FACTS:

  • Constipation is more common in pregnant than in non-pregnant women. Studies estimate that 16-39% of pregnant women experience constipation (reference).
  • The most likely causes of constipation and bloating with pregnancy are profound hormonal changes (increased progesterone levels).
  • Also, the enlarged gravid uterus may cause pressure on the intestines contributing to the development of constipation, particularly in the third trimester.
  • UTI is relatively more common in pregnant women due to the relaxation of the smooth muscles of the urethra (leading to urethral dilatation), making it easier for the bacteria to reach the bladder and the kidneys (reference).
  • Also, The pressure of the enlarged gravid uterus on the urinary bladder and the ureters may aid in the development of UTI and its complications (kidney infection or pyelonephritis).
  • According to theory (1) in the previous section, constipation may add to the pressure exerted on the urinary bladder and ureters by the gravid uterus contributing to UTI development.
  • Also, an indirect link between UTI and constipation in pregnant women exists because both share the same causes (hormonal changes leading to smooth muscle relaxation and pressure by the gravid uterus).

4. Prevention of UTI with constipation.

As we explained above, constipation may contribute to the development of UTIs in some people. So, treatment or prevention of constipation may help the prevention of recurrent UTIs.

Here are some tips:

  • Increase the fiber content of your food. This is a good resource for increasing the fiber content of food.
  • Exercise more often: sedentary lifestyle is one of the strongest risk factors for constipation. However, even walking and other low-intensity exercises help constipation prevention and relief.
  • Don’t ignore any urge to have a bowel movement. Habitual impression of the urge to poop contribute to constipation development.
  • Fiber supplements such as Metamucil also helps
  • Laxatives such as Miralax®, Dulcolax®, and Citrucel may also help in cases that don’t respond to diet, lifestyle changes, and fiber supplements.
  • If your constipation is resistant to these simple remedies and OTC laxatives, talk to your doctor about other options, such as prescription medications, pelvic training techniques, or surgical interventions.
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5. Can a UTI cause constipation?

UTI is an infection in your urinary tract (the urinary bladder or kidneys. There is no direct influence of UTI on bowel movement. However, UTIs can contribute to the development of constipation in predisposed patients as with:

  • Medications used to treat UTIs may cause constipation (Some antibiotics and nonsteroidal anti-inflammatory drugs cause constipation).
  • Patients with UTIs may suffer from anorexia and decreased food (fiber) intake, leading to constipation.
  • UTI and constipation may occur due to common causes such as pregnancy, depression, etc.

My thoughts as a nephrologist:

Both constipation and UTI are particularly common in females, each for its unique causes. The coexistence of constipation and UTI doesn’t necessarily mean one causes the other.

The links between UTI and constipation are yet to be confirmed by more thorough studies. Meanwhile, it would help if you managed each condition separately.