16. Anal and Rectal Disorders

Anal and Rectal Disorders

• These disorders encompass a range of conditions affecting the anus and rectum, including various infections, anatomical issues, and neoplasms.
• Resources and textbooks frequently cited include Robbins & Cotran, Pathologic Basis of Disease, and Schwartz's Principles of Surgery. These resources are helpful for understanding the pathophysiology, histopathology, and clinical settings of these disorders.

Anatomy: Rectum

• The rectum's longitudinal muscle fibers are dispersed to form the longitudinal layer.
• Fibers from the longitudinal layer join the circular muscle layer.
• The rectum's circular muscle layer is exposed via a window cut in its longitudinal muscle layer.
• Anatomical structures mentioned include the rectosigmoid junction, sigmoid colon, free tenia, the levator ani muscle, superficial and deep layers, subcutaneous tissue, fibrous septum, components of the external anal sphincter, corrugator cutis ani muscle, and perianal skin.

Anatomy: Annus

• Anatomical structures of the anus are mentioned, including puborectalis muscle, internal hemorrhoidal plexus, internal anal sphincter, external anal sphincter, external hemorrhoidal plexus, and anoderm.
• Structures like the column of Morgagni, dentate line, anal crypt, and anal gland are also noted.

Innervation

• The internal anal sphincter is innervated by extrinsic autonomic fibers from both the sympathetic and parasympathetic nervous systems.
• The pudendal nerve (S2, S3, and S4 sacral nerve roots) innervates the external anal sphincter.
• The sympathetic nervous system (L1, L2, and L3 pelvic plexus) and the parasympathetic nervous system (S2, S3, and S4 nervi erigentes) are involved in the innervation of the rectum.

Infectious Disorders

• Infectious diseases of the annus and rectum are addressed.
• Specific infections considered include Chlamydia, Lymphogranuloma venereum, Gonorrhea, Syphilis, and HPV (venereal warts). Relevant organisms and epidemiological factors are discussed.

Anal Fissure

• Anal fissure is a tear or ulceration of the anal canal, commonly found in young adults.
• Risk factors include constipation, high-fat diets, and conditions like Crohn's, leukemia, tuberculosis and HIV.
• Pathophysiology involves decreased blood flow to the posterior midline of the anal canal and spasm of the internal anal sphincter.
• Symptoms include pain and bleeding during or after bowel movements.

Anal Stenosis

• Anal stenosis is a narrowing of the anal canal.
• This condition can be congenital but is more commonly acquired, often following hemorrhoidectomy or other procedures.
• Factors may be excessive anal skin utilization to close the wound, tumor growth or scarring (e.g., Crohn's disease), laxative use or chronic diarrhea.
• Symptoms include difficulty passing stools, small stools, incomplete evacuation, painful defecation, and bleeding (hematochezia).
• Diagnosis often involves rectal examination, anoscopy, flexible sigmoidoscopy, colonoscopy, barium enema, or pelvic imaging, with biopsies potentially required.
• Treatment can involve stool softeners, periodic dilatation (using digital or flexible dilators), or surgery (scar removal, or sphincterotomy and anoplasty).

Anorectal Abscess

• Anorectal abscess is a pus collection in perianal, ischiorectal, intersphincteric, or supralevator spaces, likely due to infection in the anal glands.
• Factors leading to this condition include Crohn's, diabetes, heart disease, lymphoma, leukemia, anal/rectal cancer, radiation proctopathy, and infections (Chlamydia, actinomycosis, tuberculosis)
• Symptoms of anorectal abscess include pain, swelling, anal discharge, and anorectal bleeding.

Hemorrhoids

• Hemorrhoids are dilatations of anal venous structures, affecting up to 50% of adults.
• Internal hemorrhoids originate above the dentate line and are lined with rectal mucosa; external hemorrhoids originate below it and are lined with perianal squamous epithelium.
• Risk factors associated with hemorrhoids include chronic constipation, pregnancy, pelvic malignancy, chronic cough, chronic diarrhea and any conditions increasing pelvic venous pressure.
• Treatments can vary from topical local anesthetics to procedures like rubber band ligation, cryosurgery, electrocoagulation or saline injection; surgery (hemorrhoidectomy) can be necessary if needed.

Other Conditions

• Other topics addressed include anal fistula, perianal Crohn's disease, rectal prolapse, ulcerative proctitis, neoplasms of the anus, and rectal foreign bodies.
• Each condition has specific pathophysiology, symptoms, diagnosis approaches, and treatment options outlined.