Sabiston Ch50 - Small Bowel Anatomy, Physiology, Obstruction & Crohn Disease

Citation: Sabiston Textbook of Surgery, Chapter 50 “Small Intestine” (authors: Tong Gan, B. Mark Evers). Source file: raw/Sabiston Ch50 - Small Intestine.pdf, pages 1–30 of 61 (chunk 1 of the chapter).

Type: Textbook reference chapter — narrative background/orientation, not critically-appraised primary literature. Content is filed as reference and flagged as such throughout; where the chapter cites individual studies, those citations are noted but not independently appraised here.

Scope of this chunk

• Embryology (foregut/midgut/hindgut origins of the small bowel)
• Gross anatomy (duodenum, jejunum, ileum distinctions), neurovascular/lymphatic supply, microscopic anatomy (mucosa/submucosa/muscularis/serosa, villi/crypts, cell types)
• Physiology: digestion/absorption of carbohydrates, protein, fat, water/electrolytes, vitamins; motility (MMC); endocrine function (GI hormones and receptors); immune function (GALT, Peyer patches, IgA)
• Small bowel obstruction: causes (Box 50.1/Fig 50.10 — adhesions ~60%, neoplasms ~20%, hernias ~10%, Crohn’s ~5%, misc <5%), pathophysiology, clinical manifestations and diagnosis (history, exam, labs, plain film/CT/enteroclysis/MRI/ultrasound accuracy), simple vs. strangulating obstruction, treatment (fluid resuscitation, tube decompression, contrast challenge, operative vs. nonoperative management, laparoscopic management candidacy), management of specific problems (recurrent obstruction/adhesion prevention, acute postoperative obstruction, ileus)
• Crohn disease: history, incidence/epidemiology, etiology (infectious/immunologic/genetic [NOD2/CARD15, Table 50.5]/environmental factors), gross and microscopic pathology (creeping fat, skip lesions, transmural inflammation, noncaseating granulomas), Montreal classification (Table 50.6), clinical manifestations (including extraintestinal), diagnosis (serology, fecal calprotectin/lactoferrin, CTE/MRE, endoscopy including balloon enteroscopy and capsule endoscopy, CDAI [Box 50.4]), medical management (aminosalicylates, corticosteroids/budesonide, immunosuppressives, anti-TNF therapy, novel biologics, nutritional therapy, smoking cessation), and surgical treatment (indications, primary anastomosis vs. diversion decision-making, anastomotic technique debate including Kono-S anastomosis, laparoscopic approach, specific problems: acute ileitis, structuring disease [strictureplasty types and contraindications], penetrating disease/fistula, free perforation)

Key points

• Obstruction epidemiology: adhesions are by far the most common cause of small bowel obstruction (~60%), followed by neoplasms (~20%), hernias (~10%), Crohn disease (~5%), and miscellaneous causes (<5%).
• Diagnostic imaging accuracy: plain abdominal radiographs are diagnostic of obstruction in up to 86% of cases; further evaluation (CT or barium radiography) is needed in 20–30%. CT is particularly useful with a history of malignancy, postsurgical patients, or no prior abdominal surgery.
• No reliable noninvasive test for strangulation/ischemia — clinical judgment via careful history and serial exam remains central; classic signs (tachycardia, fever, leukocytosis, constant noncramping pain) do not reliably rule strangulation in or out.
• Nonoperative management of partial SBO succeeds in up to 85% of patients; complete obstruction is far less likely to resolve without surgery, and prolonged nonoperative trials risk missing an underlying strangulated obstruction (retrospective data suggest complication rates rise significantly after a 12–24 hour delay).
• Chewing gum for postoperative ileus prophylaxis: a more recent randomized trial found no benefit and suggested possible harm from the sugared gum used.
• Crohn genetics: NOD2 is the strongest and most replicated Crohn susceptibility gene; homozygosity confers a 17- to 40-fold increased risk. NOD2 is also a genetic predictor of ileal stenosis, fistula, and Crohn-related surgery.
• ~70% of Crohn patients require surgery within 15 years of diagnosis; surgery does not cure the disease. Modern surgical philosophy favors limited, bowel-length-preserving resection (inflammation-free margins, not wide “oncologic-style” margins) plus strictureplasty where possible.
• Strictureplasty is a bowel-preserving alternative to resection for fibrostenotic strictures — not mentioned in the Colon and Rectum chapter chunk that originally built the Crohn Disease page; this chunk fills that gap.
• Anastomotic technique: a French RCT found no difference in leak/complication/symptomatic recurrence rates between side-to-side stapled and end-to-end hand-sewn anastomosis, though endoscopic recurrence was slightly higher with end-to-end (43% vs. 38%). A newer antimesenteric functional end-to-end hand-sewn technique (Kono-S anastomosis) showed significantly lower stenosis and recurrence in one trial but needs further RCT confirmation.

Limitations

• Narrative textbook chapter, not a systematic review — evidence grading is inconsistent and mixes landmark historical studies with recent trials without a unified appraisal framework.
• Several claims cite single studies (e.g., chewing gum trial, hyaluronate membrane trials, Kono-S anastomosis trial) without broader corroboration; treat these as preliminary/single-source pending independent primary-literature ingest.

Relevance

Backs the new Small Intestine Anatomy & Physiology concept page, the new Small Bowel Obstruction condition page, and a substantial expansion of the existing Crohn Disease page (previously built only from Sabiston Ch52 - Inflammatory Bowel Disease and focused on colonic surgical indications/options). More chunks of this chapter to follow (remaining inflammatory/infectious diseases, neoplasms, diverticular disease, miscellaneous problems).