Next time you go to a party, try surveying people for a definition.  You’ll get a myriad of responses, none of which count.  I address the condition if a patient has a) a change in bowel habits from their norm, and b) they’re uncomfortable with it.  Maybe they have to strain, feel defecation is incomplete or whatever, but it’s new, and they don’t like it (some resort to manual removal, which is the worst).

Like any symptom, constipation can be acute or chronic, but clinically it doesn’t seem to matter.  Even though the longer it’s been going on, the more functional it’s likely to be, I tend to go through the same diagnostics, since they’re minimal.  Therapeutics are the same as well, both lifestyle changes and pharmacologics.

The main difference is that I’d rarely refer to GI for evaluation if constipation’s been present a long time.  However, it’s important to get the chronology exact.  Maybe a patient thinks they’ve never moved their bowels often enough, without realizing that their pattern has simply been a normal variant.  So now, with the significant change, they still quote a long duration.

Key question then, as always with any complaint — “Is it getting better, getting worse, or staying the same?”  New worsening would equal “acute constipation.”  But then you have to inquire about past exacerbations.  Lifelong pattern of similar “flares” becomes “chronic” once more.

That’s why I always maintain that delineating chronology is key to diagnostics.  You have to really put yourself in the patient’s shoes [or on their potty?].

Most constipation is functional.  A variety of conditions can cause constipation, such as neurologic disorders, diabetes (via its own neuropathy), pregnancy, scleroderma, etc. — but the symptom only occurs when the disease is long-standing.  They don’t present with the symptom.  Pregnancy, for example, presents with amenorrhea & eventually an enlarging uterus, not with bowel problems (although, given the power of denial, there’s always that special case of “rule-out appendicitis,” i.e. in labor, so I suppose constipation at 28 weeks might rarely be an initial concern).

Constipation — Differential Diagnosis

Common Causes of Constipation

  • Painful Anal Lesions (fissures, etc)
  • Proctitis (also painful)
  • Medications
  • Functional (incl. Irritable Bowel Syndrome)

Uncommon Causes, But Easy Rule-Outs

  • Hypothyroidism
  • Hypercalcemia
  • Diabetic Neuropathy
  • Rectal Prolapse

New Constipation >45-50 y.o. :   Colorectal Cancer

Rare Neurogenic Causes

  • Autonomic Neuropathy (incl. diabetes)
  • Hirschsprung Disease
  • Chagas Disease
  • Multiple Sclerosis
  • Spinal Cord Injury
  • Parkinson’s

Rare Non-Neurogenic Causes

  • Anorexia Nervosa
  • Pregnancy
  • Small Bowel Ileus
  • Panhypopituitarism
  • Scleroderma

Red Flags (needs colonoscopy)

Few patients with constipation require scopes.  Consider it among those with:

  • Age >45 (if had one in last 5 years, consider a flex-sig)
  • Fam Hx colorectal cancer & age >40
  • rectal bleeding without anal lesion (see below)
  • iron deficiency anemia
  • weight loss (significant)
  • obstructive symptoms

Let’s go on.

Painful Defecation

The first thing I ask is if there is anorectal pain during defecation.  If so, focal lesions like fissures are a likely culprit.  A careful anal exam is mandatory, with good lighting.  Spread & inspect every wrinkle or you’ll miss it.  Do a slow & purposeful digital exam of the anus, palpating point by point around the canal for tenderness in just one area.

Some people are tense, so any digital exam is uncomfortable & every maneuver generates a wince.  That’s not helpful.  For maximum relaxation, I usually place patients in a right-lateral almost-prone position, left (upper) knee bent, right (lower) leg relatively straight, left (“upper”) arm dangling off the table.

I’m right-handed.  If you’re a lefty, reverse it all, in left-lateral.  Texts may say “left-lateral” out of habit, but especially if the patient’s male & you also want to access the prostate, the best position allows your dominant hand (i.e. finger) to face anteriorly.

If there’s no anal tenderness, continue on in to examine the rectum.  Proctitis (uncommon) causes generalized rectal tenderness, of all four walls.  The tenderness is pretty significant.  But just to be sure that it is actually the rectum that hurts, pause without touching any wall.  Then wiggle the proximal part of your finger in each direction in the anus, without manipulating rectal tissue.  If that generates pain, it’s the anus after all, not the rectum.

Before embarking on an anorectal exam, ask if the patient [or partner] ever inserted any type of foreign body.  That way you won’t be surprised.  Also inquire about unprotected rectal sex, and anal discharge, which would increase suspicion for an STD-related proctitis.

An anorectal exam may reveal a weak sphincter (not necessarily painful).  This would generate concern for neurologic disease. An exception would be the person who’s had frequent rectal sex, in which case the finding isn’t relevant.

Non-Painful Defecation

This is usually how constipation presents.  My first question is to myself: is the patient young or old?  “Old” here means 50, i.e. colorectal cancer age, requiring colonoscopy.  Erring on the side of caution, since there’s a potential symptom, I’d even drop it to 45.

New-onset constipation in a “young” person is likely functional.  Seek a history of psychosocial changes correlating with the same time frame, things like dehydration, diet changes, emotional stresses, or other significant changes in life or lifestyle.  And just to get it out of the way, however unlikely, since bowel dysfunction is one symptom of cauda equina syndrome, you might as well ask about the others:

  • Bladder dysfunction (major urinary retention or incontinence; not just “stress” or “urge”)
  • Perineal or perianal paresthesias (numb / tingling of scrotum / labia or anus)
  • Leg weakness

Very unlikely you’d ever find anything, but a few questions are cheap & easy.  However, I wouldn’t go examining for an anal wink reflex without good indication, like objective leg weakness or DTR abnormalities.

Medications are a main cause of constipation.  The big ones are:

  • Anticholinergics (antihistamines, tricyclics, antipsychotics, “antispasmodics,” etc.)
  • Iron (including vitamins with iron that the patient didn’t know was included)
  • Aluminum-containing antacids
  • Opioids
  • Laxatives (with rebound constipation)

“Antispasmodics,” drugs like dicyclomine (Bentyl), are in quotes, because to my knowledge there’s no good evidence they work any better than placebo for any disease, condition, or symptom.  I do know of at least one patient who spent a week in the ICU for an overdose.  Anticholinergic recreational drugs (Jimson weed, etc.) also qualify (though I can’t speak to their recreational efficacy).

Don’t blame a medication they’d taken for a while without problem.  Conversely, virtually any new med might be responsible if there’s a good temporal correlation.  A discontinuation trial, if possible, with subsequent rechallenge, could be diagnostic.

An abdominal exam is usually normal.  I don’t usually do a rectal exam on the first visit on young patients with painless constipation.  It’s not wrong to, but the yield is incredibly low, unless the symptom is so exaggerated as to suspect an impaction.  History compatible with a rectal prolapse (feeling something protruding) warrants having patient strain in knee-chest position during an exam.

But no matter what, NEVER perform an exam for occult blood in the stool.  All the texts & guidelines say to, but it makes absolutely no sense to me.  The test is meant as a screen for colon cancer in persons ≥50, to be done at home.  When performed by digital exam, after manipulating tissue, in a younger patient, the likelihood of an irrelevant-positive is enormous.

Then what are you going to do with your 25 y.o.?  Refer them for colonoscopy?  Great way to lose credibility (if not get laughed about), though you’ll certainly receive a consultation report back, “Thank you for referring your interesting patient…”  And if a positive result doesn’t generate further action, why do it in the first place?  Conversely, a negative test doesn’t rule out anything.

I only check for occult blood if the patient reports “black stools,” and I want to see if there’s melena.  True melena (pure blood)  makes the guaiac card turn blue in a fraction of a second.  Anything longer isn’t melena

The only laboratory work-up I consider for constipation is:

  • TSH (for hypothyroidism)
  • Calcium (for hypercalcemia)
  • Maybe test for iron deficiency (hemoglobin / hematocrit, MCV, or serum ferritin)

So now we have a youngish patient with new-onset constipation, no clues on history, no culprit meds, normal abdominal exam, & a few normal labs.  We could diagnose Irritable Bowel Syndrome, but the various criteria for that seem to include abdominal pain (which is usually relieved by defecation).  Personally, averse to labels, if there’s no abdominal pain, I usually just diagnose “Constipation.”  May sound dumb — “Subjective: Constipation; Assessment: Constipation” — but I feel intellectually more honest.

So then we treat: stool-softeners, fiber (dietary & pharmaceutical), fluids, exercise, judicious laxatives.  Then we see them back in 3-4 weeks.  Weight loss [rare] garners a work-up, maybe CT, certainly G-I referral.

If no better, an anorectal exam is in order if not previously done.  Persistent symptoms without weight loss generates review of treatment adherence, reassurance, change stool softener to lactulose or mineral oil, & more reassurance.  Most patients respond, though sometimes you have to bail out with a G-I referral, to rule out the more obscure neurologic etiologies.

An “old” patient with new-onset constipation, not a new flare of a chronically-occurring symptom, has by definition a “change in bowel habits,” one of the 7 cardinal cancer symptoms.  They warrant an abdominal & rectal exam (rule out impaction, which usually requires ER or hospitalization), as well as colonoscopy.  If they’d had a recent scope, follow the work-up for our “young patient;” if no improvement, a flexible sigmoidoscopy and G-I referral are in order.


Patients < 45 y.o.

If Red Flags (wt. loss, painless bleeding w/o anal lesion)  >>>  Colonoscopy

If Cauda Equinae Symptoms  >>>  to ER

1.  If painful defecation >>>  Careful anorectal exam for fissures / lesions, proctitis

2.  If taking a possibly-related medication  >>>  Try discontinuation & rechallenge (if possible)

3.  None of above  >>>  Treat (lifestyle changes, stool softeners, fiber, judicious laxatives)

4.  If no change:

  • anorectal exam if not done
  • Labs:  TSH, Calcium, CBC / serum Ferritin
  • Reassure & intensify treatment

5.  Still no change  >>>  Refer to G-I

Patients > 45 y.o.

Same as above

Need colonoscopy if due, or flex-sig

A Case

A 79 y.o. Latina woman had new onset “diarrhea.”  History was remarkable only for well-controlled HIV infection, & hyperlipidemia.  Abdominal exam revealed a left lower quadrant mass; on CT, the rectum was distended to 28 cm., full of stool.  So the “diarrhea” was leakage around an enormous fecal impaction.

The patient was disimpacted, once in an ER and again by G-I.  Colonoscopy was normal.  Chagas serology was negative.  A bowel regimen was begun.  The TSH was 5.9, a month later it was 11.6 with a Free T4 of 0.7 (0.8 = lower limit of normal).

I see all sorts of asymptomatic patients with TSH’s higher than that, though their T4’s are usually normal.  Hers was just slightly low.  But she’s 79-years-old; who knows if at that age, even minimal hormonal changes can cause such dramatic effects.

I treated her, with L-thyroxine 25 mcg daily, and she did well.  But I’m gradually increasing the dose, to get her TSH <2.5.  The “4.5 = upper limit normal” is simply population-based.  My endocrinology consultant says that really it should be 2.5.  Given her degree of illness, I’ll aim for ideal control.

And that’s it for constipation.  Since we’re in the area, next topic will be a very brief discussion of Anal Itching, with a somewhat bizarre case.

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