Constipation: Types, Rome IV Criteria, Transit Time, and IBS

1. Definition of Constipation

• Straining (52%)
• Hard stools (44%)
• Inability to have a bowel movement (34%)

2. Types of Constipation

A. Secondary Constipation

• Medications: Opioids, anticholinergics, calcium channel blockers, iron, antidepressants
• Endocrine/Metabolic: Hypothyroidism, hypercalcemia, diabetes mellitus (mean colonic transit time significantly prolonged in diabetics - 34.9 ± 29.6 hours vs. controls)
• Neurological: Parkinson's disease, multiple sclerosis, spinal cord lesions
• Structural/Mechanical: Colorectal cancer, strictures, rectocele
• Dietary/Lifestyle: Low-fiber diet, dehydration, immobility

B. Primary (Functional) Constipation - Three Subtypes

• Results from intrinsic dysmotility of the colon with significant impairment of propulsive colonic motor activity
• High-amplitude propagated contractions (HAPCs) are reduced in frequency and duration
• Some patients have no peristaltic movement over 24 hours; others have fewer and shorter movements than controls
• May involve only the colon or the entire GI tract
• Patients may go days to weeks without bowel movements despite using laxatives and enemas
• Pathology: Reduced numbers and abnormal morphology of interstitial cells of Cajal (ICCs), decreased substance P, increased VIP and nitric oxide in myenteric plexus; the predefecatory period (gastrocolic reflex) is blunted or absent

• Stool traverses the colon at a normal rate; stool frequency may even be normal
• Patients feel constipated - report hard stools, difficult defecation, bloating, and abdominal pain relieved by defecation
• Significant overlap with IBS-C (constipation-predominant IBS)
• Psychological factors play a larger role; often associated with altered visceral sensation

• Caused by failure of coordinated pelvic floor relaxation during defecation (dyssynergic defecation / anismus)
• Also includes mechanical causes: rectocele, enterocele, sigmoidocele, rectal intussusception, full-thickness rectal prolapse, solitary rectal ulcer syndrome
• These disrupt the coordinated transit of stool through the rectum
• A specific subtype - dyssynergic defecation - is defined by paradoxical contraction (or <20% relaxation) of the anal sphincter during defecation attempts

3. Rome IV Criteria

Rome IV Criteria for Functional Constipation

Must include 2 or more of the following (present for the last 3 months, with symptom onset at least 6 months before diagnosis):

• Loose stools are rarely present without the use of laxatives
• There are insufficient criteria for IBS (pain is not a predominant feature)

Rome IV Diagnostic Criteria for Dyssynergic Defecation

1. Diagnostic criteria for functional chronic constipation (Rome IV)
2. Dyssynergia demonstrated during repeated attempts to defecate: paradoxical increase in anal sphincter pressure (contraction) OR <20% relaxation of resting pressure, on manometry/imaging/EMG
3. One or more of:
   • Inability to expel an artificial stool (50 mL water-filled balloon) within 1 minute
   • Prolonged colonic transit time (>5 markers retained / ≥20% retention on plain X-ray at 120 hours after ingesting one Sitzmarks capsule)
   • Inability to evacuate or ≥50% retention of barium during defecography

4. Colonic Transit Time

A. Radiopaque Marker Testing (Sitzmarks)

• Method: Patient ingests plastic beads/rings (24 markers); plain abdominal X-ray at 5 days (120 hours)
• Normal: >80% of markers passed (i.e., <5 markers / <20% retained) by day 5
• Slow transit: ≥5 markers retained, scattered throughout colon
• Outlet obstruction: Markers converge in sigmoid/rectum
• Normal mean colonic transit time: 30-40 hours; upper limit of normal = 72 hours
• Women often have longer maximal transit times than men (70-106 hours vs. 50 hours)
• Patient must be on high-fiber diet; must avoid laxatives/enemas before study

B. Wireless Motility Capsule (SmartPill)

• Method: Patient swallows a capsule after a standardized meal; the capsule measures temperature, pH, and pressure continuously as it travels the GI tract; data receiver worn for up to 5 days
• Gastric emptying determined by rise in pH (entry into duodenum); entry into colon marked by drop in pH
• Also measures gastric emptying time and small bowel transit time
• Normal colonic transit time: 10-59 hours
• Abnormal (delayed): >44 hours in men, >59 hours in women
• No radiation exposure
• Specificity 0.95, sensitivity 0.46 for identifying abnormal transit

C. Scintigraphy

• Uses radiolabeled isotopes to track stool movement in real time through the colon
• Allows assessment of segmental colonic transit
• Quantitative and functional but involves radiation; less widely available

5. IBS (Irritable Bowel Syndrome)

Rome IV Criteria for IBS

Recurrent abdominal pain, on average at least 1 day per week in the last 3 months, associated with 2 or more of the following:

1. Related to defecation
2. Associated with a change in frequency of stool
3. Associated with a change in form (appearance) of stool

• Criteria fulfilled for the previous 3 months, with symptom onset at least 6 months before diagnosis
• Abdominal pain is mandatory - IBS should NOT be diagnosed in its absence

IBS Subtypes (Based on Bristol Stool Form Scale)

Historical Diagnostic Criteria for IBS

Manning Criteria (1978) - Positive diagnosis requires ≥3 of 6:

1. Abdominal distention
2. Abdominal pain eased after bowel movement
3. Feeling of incomplete emptying
4. Looser stools at onset of abdominal pain
5. More frequent bowel movements at onset of abdominal pain
6. Mucus per rectum

Kruis Criteria (1984) - Score-based; IBS excluded if any physical finding or lab abnormality:

• Patient history: abdominal pain, flatulence, irregularity, mixed diarrhea/constipation, pellet stools/mucus, symptoms >2 years
• Physician assessment: no abnormal findings, normal ESR, normal CBC, no blood in stool

Pathophysiology of IBS

• IBS-D: Increased high-amplitude propagated contractions, enhanced gastrocolic reflex, rectal hypersensitivity
• IBS-C: Increased segmental (non-propulsive) contractions, decreased HAPCs, reduced rectal sensation
• Colonic and small bowel transit are delayed in IBS-C and accelerated in IBS-D
• Autonomic dysfunction: sympathetic adrenergic dysfunction in diarrhea; vagal dysfunction in constipation

• Balloon distention of the rectum induces pain at lower volumes in IBS patients (up to 60% of patients)
• Serves as a potential biomarker; explains awareness of bowel activity and urgency

• Altered central pain processing (central sensitization)
• Psychological stress exacerbates symptoms; anxiety and depression are common comorbidities

• Occurs after acute gastroenteritis (bacterial, viral, parasitic)
• Risk factors: female sex, prolonged illness, psychological distress at time of infection, elevated mucosal inflammatory markers
• Mediated by increased mucosal enterochromaffin cells, increased 5-HT, altered microbiome

• Dysbiosis documented; role in symptom generation under active investigation

• 95% of serotonin is in the gut (enterochromaffin cells)
• 5-HT4 agonists (e.g., prucalopride) help IBS-C; 5-HT3 antagonists (e.g., alosetron) help IBS-D

IBS: Alarm Features (Red Flags - require further investigation)

• Rectal bleeding
• Unexplained weight loss
• Iron deficiency anemia
• Nocturnal symptoms (40% of IBS patients report this, but low PPV for organic disease)
• Onset after age 50 (OR 2.65 for organic disease)
• Family history of colon cancer, IBD, or celiac disease

IBS vs. Functional Constipation: Key Distinction

• Sleisenger and Fordtran's Gastrointestinal and Liver Disease, pp. 271-284, 2469-2473
• Yamada's Textbook of Gastroenterology, 7th ed., pp. 730, 1465-1466
• Sabiston Textbook of Surgery, 28th ed., p. 2174
• Rome IV: Mearin F, Lacy BE, Chang L, et al. Gastroenterology 2016;150:1393-1407