Obstructed defecation

Did You Know?

• The suffix '-cele' comes from ancient Greek meaning 'tumor', 'hernia', 'swelling', or 'cavity'.
• A cul-de-sac hernia (peritoneocele) is a herniation of peritoneal folds into the rectovaginal septum that does not contain other abdominal organs.
• The pelvic floor can be divided into four compartments: anterior (urinary), middle (genital), posterior (anus, anal canal, sigmoid, rectum), and peritoneal.

Definitions and terminology

Constipation is divided into primary and secondary groups. Primary constipation arises from disrupted neuromuscular regulation of the colon and rectum or brain–gut neuroenteric function, while secondary constipation results from diet, drugs, behavioral, endocrine, metabolic, neurological, or other disorders. Recognized subtypes of primary constipation include dyssynergic defecation, slow transit constipation, and irritable bowel syndrome with constipation, though overlap exists. Obstructed defecation syndrome (ODS) is a loose term encompassing a constellation of symptoms caused by multiple, complex, and poorly understood functional and organic disorders. Terminology and classification in the literature are confused; some sources inappropriately treat ODS as a synonym for anismus, though anismus is only one cause. Other authors use ODS to refer to defecatory dysfunction without pathological findings. The ICD-11 and Rome-IV classifications do not use the term ODS, instead referring to functional defecation disorders, a classification criticized as ambiguous and symptom-based rather than etiopathological. One publication suggested using the descriptive term evacuation disorders, subclassified to include all contributory factors.

Causes

Causes of ODS are grouped into functional (physiologic) disorders and mechanical (anatomic/organic) disorders, and can also be classified into four groups. Functional outlet obstruction includes inefficient inhibition of the internal anal sphincter (e.g., short-segment Hirschsprung's disease, Chagas disease, hereditary internal sphincter myopathy) and inefficient relaxation of the striated pelvic floor muscles (e.g., anismus, multiple sclerosis, spinal cord lesions). Mechanical outlet obstruction includes internal rectal prolapse, enterocele, sigmoidocele, rectal or anal cancer, and anal stenosis. Dissipation of force vector includes rectocele, descending perineum syndrome, and rectal prolapse. Impaired rectal sensitivity includes megarectum and rectal hyposensitivity. Dyssynergic defecation (anismus) is defined as failure of the striated pelvic floor muscles to relax appropriately during attempted defecation; in extreme cases, paradoxical contraction occurs. ODS may also be associated with solitary rectal ulcer syndrome. A sigmoidocele is a protrusion of peritoneum containing a loop of sigmoid colon; an omentocele contains omentum. These may be internal or external.

Diagnosis

Diagnosis is challenging because most patients complain only of constipation. Many causes of ODS may coexist, and ODS can occur with slow-transit constipation. The first step is identifying organic causes and possible slow transit constipation. Patients may be too embarrassed to discuss symptoms like digitation. Two key features are inability to voluntarily evacuate rectal contents and normal colonic transit time with delayed transit in the rectum and sigmoid colon. Scoring systems assess severity and measure treatment outcomes. The Renzi ODS score is a validated five-item questionnaire covering excessive straining, incomplete evacuation, use of enemas or laxatives, vaginal-anal-perineal digitations, and abdominal discomfort or pain. The Altomare ODS score has seven parameters scored 0–4: mean time spent at the toilet, number of daily defecation attempts, anal or vaginal digitation, use of laxatives, use of enemas, incomplete or fragmented defecation, and straining at defecation.

Treatment

Obstructed defecation can be difficult to manage even for experienced clinicians. A multidisciplinary approach is suggested, involving a gynecologist or urogynecologist, gastroenterologist, and colorectal surgeon. The general goal is to improve defecation mechanics and stool texture, which markedly improves quality of life. Treatment may be conservative or surgical, but the exact approach is controversial. Many authors oppose surgery as first-line treatment, while others consider it a last resort or not at all. Underlying causes are typically psychological, muscular, or neurological, requiring complex long-term treatment. Some suggest that surgically correctable anatomical disorders may be effects rather than causes of ODS. Both patients and surgeons often prefer faster surgical solutions, which may explain why most surgical procedures are unsuccessful long term. Most authors now recommend a combination of conservative measures, with surgery as a secondary treatment when strictly indicated. For isolated dyssynergic defecation without anatomical defect, surgery is contraindicated; for neoplastic tumor or external prolapse, surgery is usually strongly indicated. Clinicians should set realistic and honest goals with patients.