Pelvic Floor and Anorectal Disorders: Pelvic Floor Disorders: Refractory Constipation

0:00Welcome to Board Pearls. This is episode two of three of the Pelvic Floor and Anorectal Disorders chapter, in the Colorectal and Pelvic Floor Disorders module. This episode covers the constipation mechanisms the standard drugs can't fix. A man who strains and feels blocked has dyssynergic defecation, and his case shows what goes wrong at the outlet, the bedside clue, which tests screen and confirm, and why biofeedback works where laxatives don't. A woman with lifelong constipation and a dilated colon shows the manometry finding that means Hirschsprung disease. A woman who goes once every eight to ten days and has been referred for colectomy has slow-transit constipation, and her case shows why it's diagnosed only after the outlet is cleared, how the marker study works, and who benefits from surgery. A man with slow transit and nausea shows why generalized dysmotility rules surgery out. A man constipated on chronic opioids shows why tolerance never develops and how the gut-only opioid blockers spare pain control. And a woman having bowel surgery shows the one opioid blocker that belongs only in the hospital.

1:08Here's the first patient. A forty-one-year-old man has had constipation for six years. He strains for long periods, often feels blocked, and sometimes presses on his perineum to finish. Psyllium, polyethylene glycol, senna, and linaclotide didn't help the straining. The higher doses gave him urgency and a few episodes of leakage. He has no alarm features, and his colonoscopy two years ago was normal.

1:37Prolonged straining, a sense of blockage, perineal pressure to finish, and failure of every laxative suggest a defecatory disorder, most likely dyssynergic defecation, the dominant subtype. A defecatory disorder is considered in any constipated patient who has failed empiric therapy, because the problem is mechanical, not a problem of transit. During the abdominal push, the puborectalis and external anal sphincter should relax. In dyssynergia they fail to relax or paradoxically contract, narrowing the anorectal angle and raising anal canal pressure, so stool can't exit even when the colon propels it normally. It's partly behavioral, often from inappropriate straining patterns learned over years.

2:17That mechanism explains why his laxatives failed and why he leaked. Escalating laxatives in dyssynergia produces overflow, urgency, and sometimes incontinence without solving the problem, because looser stool pushes harder against an outlet that's still closed. The right intervention is biofeedback, not another laxative, so the diagnosis has to be made before more drugs are tried.

2:42Confirming it follows a set order, and the order protects him from the wrong operation. Empiric therapy comes first, which he's had. Then come a digital rectal exam, balloon expulsion as the screening study, and anorectal manometry and defecography to confirm when balloon expulsion is abnormal, with biofeedback as treatment once the diagnosis is confirmed. A transit study comes only after a defecatory disorder is excluded. Stool backed up behind a closed outlet makes the transit study falsely abnormal, and that can push a patient toward a colectomy he doesn't need.

3:15His rectal exam gives the bedside clue. With a finger in the anal canal, the patient is asked to bear down as if passing stool. Normally the sphincter and puborectalis relax around the finger. In him they tighten, a paradoxical contraction, which supports dyssynergia but doesn't prove it.

3:34Because the exam only suggests it, he needs the screening test. In the balloon expulsion test, a balloon is placed in the rectum and filled with fifty milliliters of warm water, and he's asked to expel it while seated on a commode in privacy. Failure within sixty seconds is abnormal. Older teaching used one to two minutes, but the American College of Gastroenterology, ACG, guideline uses one minute. It's simple, inexpensive, and portable, and it's the first-line screen. He can't pass the balloon in three minutes.

4:06His abnormal balloon test leads to anorectal manometry, the main diagnostic test, which measures the muscles at rest, on squeeze, and on push. Resting anal pressure reflects the internal anal sphincter, mostly smooth muscle under sympathetic and intrinsic control, holding the canal closed at rest. Squeeze pressure reflects the external anal sphincter and puborectalis, voluntary skeletal muscle under somatic control. The push, or simulated defecation, tests whether abdominal effort is coordinated with anal relaxation. In dyssynergia, anal pressure rises rather than falls during the push, the defining manometric finding.

4:47Manometry also records two reflex and sensory measures that can change the diagnosis. The rectoanal inhibitory reflex is reflex relaxation of the internal sphincter when the rectum is stretched. Rectal sensation thresholds are recorded too. Reduced sensation suggests a megarectum or a sensory deficit, and increased sensation suggests visceral hypersensitivity, which drives urgency and incontinence rather than constipation.

5:13His manometry shows anal pressure rising during the push, normal resting and squeeze pressures, and a present rectoanal inhibitory reflex. His sphincters are strong, so his leakage was overflow of liquid stool behind a closed outlet, not sphincter weakness. It should resolve once the coordination is fixed and the laxatives are reduced.

5:33His two abnormal studies are enough to make the diagnosis, though manometry by itself wouldn't have been. Under the ACG guideline, manometry alone, without an abnormal balloon expulsion, isn't sufficient. The diagnosis needs at least two of three positive studies: anorectal manometry, defecography, and balloon expulsion. He has an abnormal balloon expulsion and an abnormal manometry, so he has dyssynergic defecation.

5:59Defecography is the third study, and it adds a picture of the anatomy that the other two can't give. In barium defecography, thickened barium paste in the rectum is expelled on a special commode under fluoroscopy. It shows dyssynergia directly, with an anorectal angle that fails to open and a puborectalis that keeps indenting the rectum during the push. It also shows structural problems: a rectocele, an anterior bulge of the rectovaginal septum that can trap stool; an enterocele, small bowel descending into the cul-de-sac; rectal intussusception; rectal prolapse; and excessive perineal descent.

6:36Magnetic resonance defecography is an alternative without radiation, increasingly preferred at centers that have it. It shows the bladder, uterus, vagina, and levator ani at the same time. So dynamic pelvic magnetic resonance imaging, MRI, is especially useful when constipation overlaps with urinary or genital prolapse, because the whole pelvic floor is examined in one study.

7:00His treatment isn't a drug. Biofeedback is first-line for anyone meeting criteria for dyssynergic defecation. Manometry probes display his anal pressures in real time while a trained therapist coaches him to relax the puborectalis and external sphincter while pushing with his abdominal wall, retraining the coordinated relaxation. A typical course is six to twelve sessions over several weeks. Randomized trials show response rates of seventy to eighty percent, substantially higher than laxatives in this group, with benefit lasting years.

7:32Biofeedback works only where the lesion is at the outlet. It doesn't work in slow transit without dyssynergia, because nothing at the outlet needs retraining. He completes eight sessions. His straining resolves, he no longer needs perineal pressure, the leakage stops, and he comes off linaclotide. If his movements had stayed infrequent after biofeedback opened his outlet, a transit study would then be interpretable.

7:57The rectoanal inhibitory reflex on manometry can point somewhere rarer, and the second patient shows it. A thirty-six-year-old woman has had severe constipation all her life. Imaging shows a markedly dilated colon above a narrowed segment, and her manometry shows no rectoanal inhibitory reflex. That points to late-onset Hirschsprung disease. Absence of the reflex is its hallmark, because the distal bowel lacks ganglion cells, so the internal sphincter never relaxes when the rectum fills. It's rare in adults, and lifelong constipation, a dilated colon above a narrowed segment, and an absent reflex together mark it.

8:34The third patient's outlet works, and her problem is the colon itself. A twenty-seven-year-old woman has had one bowel movement every eight to ten days for years. Fiber, polyethylene glycol, senna, bisacodyl, linaclotide, and lubiprostone have all failed. She has bloating but no dominant abdominal pain, and no nausea or early fullness. She's been referred for colectomy, and the surgeon wants a gastroenterology review first.

9:00Movements every eight to ten days despite every laxative suggest slow-transit constipation. Slow transit is reduced colonic propulsion. The colon has fewer high-amplitude propagated contractions a day and a blunted response to meals through the gastrocolic reflex, to cholinergic stimulation, and to stimulant laxatives, which is why higher stimulant doses don't rescue it. Surgical specimens from severe slow transit, sometimes called colonic inertia, show fewer interstitial cells of Cajal in the myenteric plexus and fewer enteric neurons, but that's a research finding, not a diagnostic test.

9:36Before her colon is blamed, her outlet is tested, because slow transit is a diagnosis of exclusion. It's made only after a defecatory disorder has been ruled out. The most common pitfall before colectomy is operating on unrecognized dyssynergia. The outlet stays closed after the colon is removed, and the patient ends up incontinent without relief. She expels the balloon in thirty seconds, and on manometry her anal pressure falls normally during the push. Her outlet works.

10:05With the outlet cleared, her transit is measured. The first-line test is the radiopaque marker study, also called the Sitz marker study or the Hinton test. On day zero she swallows one capsule containing twenty-four markers. She takes no laxatives, enemas, or motility-active drugs, and has an abdominal x-ray on day five. Retention of more than five markers, more than twenty percent, indicates slow transit. The Metcalf protocol is a variant that uses twenty-four markers daily for three days, with films on days four and seven.

10:36The test is simple and inexpensive, but two things can mislead it. It depends on the no-laxative window, so a dose of senna on day three invalidates it, and it involves a small radiation dose. And the pattern matters as much as the count. Markers scattered through the colon suggest colonic inertia, reduced propulsion throughout. Markers clustered in the rectosigmoid suggest outlet dysfunction and send the workup back to defecatory testing. Her day-five film shows eighteen markers scattered throughout the colon, slow transit in the pattern of colonic inertia.

11:09Two other transit tests exist for patients whose slowing may not be confined to the colon. The wireless motility capsule records pH, pressure, and temperature as it passes through the gut. It reports gastric emptying, small bowel transit, colonic transit, and whole-gut transit separately, which helps when slow transit may overlap with gastroparesis or generalized dysmotility. The original device is off the United States market, a successor is emerging, and insurance coverage has limited its use. Colonic scintigraphy, with gamma camera images of an oral isotope at twenty-four, forty-eight, and seventy-two hours, is used at academic centers.

11:50Confirmed slow transit still doesn't mean surgery, because medical therapy has to be exhausted first. That means an adequate trial of fiber, polyethylene glycol, stimulants, and the Food and Drug Administration, FDA, approved drugs: lubiprostone, linaclotide, plecanatide, and prucalopride. She's never tried prucalopride, the drug most suited to her deficit. Its serotonin four agonism stimulates the high-amplitude propagated contractions her colon lacks.

12:21If single drugs fail, there are still options short of colectomy. Refractory disease can be managed with combinations such as prucalopride plus a secretagogue, scheduled enemas, or a maintenance regimen tailored to the patient. Sacral nerve stimulation has mixed results in slow transit and isn't standard care for it. An antegrade continence enema through a Malone-type appendicocecostomy, which lets the patient flush the colon from above, is used in selected patients, particularly children and patients with neurogenic bowel.

12:52She starts prucalopride two milligrams daily, and after a month she goes every four to five days. Linaclotide is added back, her movements improve to every two to three days, her bloating eases, and she continues medical therapy without surgery.

13:07Had she failed everything, colectomy would have helped only if she met narrow criteria. The operation is subtotal colectomy with ileorectal anastomosis. It's for severe, disabling symptoms refractory to all medical therapy, with slow transit objectively confirmed on a marker study and a defecatory disorder excluded by manometry and balloon expulsion. It shouldn't be offered with prominent abdominal pain, which often persists afterward. It shouldn't be offered with generalized gastrointestinal, GI, dysmotility, such as delayed gastric emptying or small bowel dysmotility, because the small bowel can't compensate, or with chronic intestinal pseudo-obstruction.

13:48Even in the right patient, the results of colectomy are mixed. In published series, reoperation rates are thirty-five to forty percent, and more than half of patients have persistent abdominal pain. Bloating is common, and many patients aren't fully satisfied despite more frequent movements. Surgery usually makes patients go more often but may not make them feel well.

14:10The fourth patient shows how generalized dysmotility rules surgery out. A thirty-three-year-old man has slow transit with scattered markers and a normal balloon expulsion and manometry. He also has nausea, early fullness, and delayed gastric emptying. Removing his colon would leave a small bowel that can't compensate, so his treatment stays medical. A wireless motility capsule could measure his gastric, small bowel, and colonic transit in one study. Every patient with slow transit is asked about nausea, early fullness, and vomiting before any talk of an operation.

14:42The fifth patient's constipation has a cause outside the colon's own function, and it needs a different drug class. A fifty-six-year-old man has chronic low back pain after two spinal fusions and has taken oxycodone, about sixty milligrams a day, for three years, with controlled pain. His constipation began soon after the opioids and has steadily worsened, to two hard stools a week, with straining, bloating, and incomplete emptying, despite daily polyethylene glycol and senna. He has no vomiting or distension, and an abdominal x-ray shows stool but no obstruction. His creatinine is normal, and he takes no other regular medications.

15:22Constipation that began with the opioids and worsens despite laxatives, with no obstruction, is opioid-induced constipation. Opioids bind mu-opioid receptors on enteric neurons throughout the gut wall. That suppresses acetylcholine release from the cholinergic nerves that drive the gut, reduces propagated peristaltic contractions, increases non-propulsive segmenting contractions, and increases anal sphincter tone. Transit slows, stool dries out from prolonged water absorption, evacuation gets harder, and the patient bloats.

15:59His constipation has worsened over three years, and tolerance explains why. Tolerance develops to the analgesic effect of opioids but not to the constipating effect, so the constipation persists and worsens over chronic therapy. It's dose-related and time-dependent, and it develops in roughly forty to fifty percent of patients on chronic opioids.

16:18Treatment starts with the opioid itself. If the pain condition allows, the opioid is tapered or rotated, but his pain team wants him on his current dose. Standard laxatives, meaning stool softeners, polyethylene glycol, and stimulants, are first line for prevention and treatment. The American Gastroenterological Association, AGA, guideline emphasizes trying them first, because many patients respond. He's failed them.

16:46His next step is a drug that blocks opioids in the gut without blocking his pain relief. The peripherally acting mu-opioid receptor antagonists, PAMORAs, are structurally modified so they cross the blood-brain barrier poorly. Some carry a permanent charge, and others are pumped out of the brain by P-glycoprotein. They reach the mu receptors in the gut wall without central antagonism, so they don't cause withdrawal or reverse analgesia. They're second-line therapy, after standard laxatives.

17:14There are three PAMORAs for chronic opioid-induced constipation, and their doses and rules decide which fits him. Naloxegol is naloxone with a polyethylene glycol chain, twenty-five milligrams once daily on an empty stomach. The dose is reduced to twelve and a half milligrams with a creatinine clearance under sixty milliliters a minute or with a moderate inhibitor of the liver enzyme cytochrome P450 3A4, CYP3A4. Strong CYP3A4 inhibitors, such as clarithromycin and ketoconazole, and strong inducers, such as rifampin, are contraindicated.

17:49The other two have different forms and approvals. Methylnaltrexone is a quaternary ammonium derivative of naltrexone with a permanent positive charge. It's given subcutaneously every other day, twelve milligrams at or above sixty-two kilograms and eight milligrams below, or daily in palliative care, and an oral form is given as four hundred fifty milligrams daily. It's approved for chronic non-cancer pain and for palliative care patients with advanced illness who failed laxatives. Naldemedine, zero point two milligrams once daily, is derived from naltrexone with a side chain that prevents brain penetration, and it's approved for chronic non-cancer pain. All three commonly cause abdominal pain, diarrhea, and nausea.

18:33Before any of them, one contraindication has to be excluded: suspected or known mechanical GI obstruction. A PAMORA unmasks the gut's propulsive force above the obstruction, and perforation has been reported. Advanced cancer, peritoneal carcinomatosis, recent GI surgery, and Ogilvie syndrome, which raise the risk of a compromised bowel wall, rule these drugs out or call for careful evaluation. His x-ray shows no obstruction, and he has no distension, vomiting, bowel surgery, or cancer.

19:07All three PAMORAs are approved for his chronic non-cancer pain, he prefers a pill, his creatinine is normal, and he takes no interacting drugs, so naloxegol at full dose fits. Clarithromycin would make naloxegol contraindicated while he took it, and an inability to take pills would point to subcutaneous methylnaltrexone dosed by weight. He starts naloxegol twenty-five milligrams each morning on an empty stomach. Within a week he has a soft stool most days, mild cramping fades, and his pain control is unchanged.

19:39When a PAMORA isn't tolerated or is contraindicated, another mechanism is used. Lubiprostone is approved for opioid-induced constipation at twenty-four micrograms twice daily, because its chloride channel mechanism doesn't depend on enteric opioid signaling. Linaclotide and prucalopride aren't specifically approved for opioid-induced constipation, but they're used when it overlaps with another constipation phenotype.

20:03One drug in the same class has an entirely different indication, and the sixth patient shows it. A sixty-eight-year-old woman is having a partial colectomy with primary anastomosis and will get perioperative opioids. Alvimopan is FDA approved to accelerate recovery of GI function after partial bowel resection with primary anastomosis, preventing the prolonged ileus that surgery and perioperative opioids produce together. Its mechanism is the same enteric mu-receptor blockade.

20:32Its use is tightly limited because of a cardiovascular signal. Long-term outpatient use in chronic non-cancer pain showed an excess of myocardial infarction in a twelve-month trial. So it's restricted to short-term inpatient use, no more than fifteen doses, roughly seven days of twice-daily dosing, under a Risk Evaluation and Mitigation Strategy program. She gets it in the hospital only. It isn't continued at home and is never used for chronic opioid-induced constipation, and for the chronic PAMORAs, recent bowel surgery is a reason for caution.

21:05Here are the traps the boards set in these patients. A patient who strains and feels blocked doesn't get escalating laxatives. The digital rectal exam isn't skipped. Dyssynergia isn't diagnosed from manometry alone, because two of three studies are needed. The balloon cutoff is one minute, not two. A transit study isn't ordered before a defecatory disorder is excluded, and unrecognized dyssynergia is never sent to colectomy. Biofeedback isn't offered for slow transit without dyssynergia. And an absent rectoanal inhibitory reflex isn't overlooked, because it suggests Hirschsprung disease.

21:41The slow transit traps follow. Laxatives taken during the marker study invalidate it. Rectosigmoid clustering isn't called colonic inertia, because it points back to the outlet. Prucalopride isn't skipped before surgery. Sacral nerve stimulation isn't standard care for slow transit. And colectomy isn't offered with dominant abdominal pain, generalized dysmotility, or pseudo-obstruction.

22:04The opioid traps close the list. Tolerance to opioid constipation doesn't develop. A PAMORA doesn't come before standard laxatives. A PAMORA isn't given with suspected obstruction, and carcinomatosis, recent bowel surgery, and Ogilvie syndrome call for caution. Naloxegol's dose is cut for renal impairment or a moderate CYP3A4 inhibitor, and strong inhibitors and inducers are contraindicated. A PAMORA doesn't reverse pain control. And alvimopan is never prescribed for chronic opioid-induced constipation.

22:37So, start to finish. Suspect a defecatory disorder when laxatives fail, and look for it before testing transit. A digital rectal exam can show paradoxical contraction, and a fifty-milliliter balloon not expelled within sixty seconds screens. Manometry and defecography confirm, with two of three studies needed. An absent rectoanal inhibitory reflex suggests Hirschsprung disease. Biofeedback, six to twelve sessions, treats dyssynergia and works in most patients.

23:06Slow transit is diagnosed only after the outlet is cleared. More than five of twenty-four markers on day five confirms it, and rectosigmoid clustering points back to the outlet. Exhaust medical therapy, especially prucalopride, and reserve subtotal colectomy for disabling refractory disease without dominant pain or generalized dysmotility, knowing outcomes are mixed.

23:28Opioid constipation never develops tolerance. Start with standard laxatives, then add a PAMORA, never with obstruction, with lubiprostone as an alternative. Keep alvimopan for short inpatient use after bowel resection.

23:44Episode three moves to the anal canal itself: fecal incontinence, hemorrhoids, anal fissure, and pruritus ani.

23:53For the full chapter, the practice vignettes, and the topic-tagged question bank, head to board pearls dot com. You'll find the rest of the series on Apple Podcasts, Spotify, or wherever you listen to podcasts. That brings us to the end of episode two of three of chapter sixteen, and I'll see you in the next one.