Which of the following is true about chromic catgut?

Correct Answer: D. It is absorbed by enzymatic degradation and macrophage phagocytosis

Chromic catgut is an absorbable suture material derived from the submucosa of sheep or cattle intestines (not cat gut—a historical misnomer). The "chromic" designation refers to the tanning process using chromium salts (not nickel), which cross-links collagen fibers and delays absorption compared to plain catgut. The mechanism of absorption is dual: enzymatic degradation by tissue proteases (collagenase, elastase) breaks down the collagen matrix, while macrophages infiltrate and phagocytose the degraded fragments. This process typically takes 90–120 days in vivo, making chromic catgut suitable for subcuticular and mucosal closures where early suture removal is impractical. In Indian surgical practice, chromic catgut remains a standard choice for gynecological, pediatric, and mucosal repairs despite the availability of synthetic absorbables, due to cost-effectiveness and predictable absorption kinetics. The inflammatory response is minimal compared to non-absorbable materials, reducing foreign-body granuloma formation.

Why the other options are wrong

A. It is made from cat gut — This is a common misconception perpetuated by the historical name. Catgut is actually derived from the submucosa of sheep or cattle intestines, never from cats. The term 'catgut' likely originated from 'kit gut' (kit being a stringed instrument) or a corruption of 'cattlegut.' This trap tests whether students know the true source material rather than relying on the misleading name. B. It is tanned with nickel salts to improve handling and to resist degradation in tissue — This is factually incorrect on two counts: chromic catgut is tanned with chromium salts (chromium trioxide or chromium chloride), not nickel salts. The chromium cross-links collagen and delays absorption to ~90–120 days. Nickel tanning is not used in surgical sutures and would introduce unnecessary toxicity. This option conflates the tanning agent with an incorrect metal. C. It is made from rabbit gut — Rabbit gut is not used for catgut suture manufacture. The standard sources are sheep or cattle submucosa, chosen for their collagen quality and availability. Rabbit intestines lack the structural integrity and consistent diameter needed for reliable suture production. This is a distractor that tests source material knowledge alongside option A.

High-Yield Facts

Mnemonics

CAT-GUT Absorption Chromium tanning → Absorption by Tissue enzymes + macrophage GUT-phagocytosis. Remember: Chromium (not nickel), Absorption (enzymatic + phagocytic), Tissue source (sheep/cattle, not cat). Chromic vs. Plain Catgut Chromic = Chromium-tanned, delayed absorption (90–120 days). Plain = untanned, rapid absorption (7–10 days). Use chromic for subcuticular; plain for mucosal where quick absorption is desired.

NBE Trap

NBE exploits the misleading name 'catgut' to lure students into selecting option A (cat gut) or option C (rabbit gut), testing whether they know the true source material (sheep/cattle) rather than relying on the historical nomenclature. The nickel salt distractor (option B) tests knowledge of the specific tanning agent (chromium, not nickel).

Clinical Pearl

In Indian operating theaters, chromic catgut remains the workhorse absorbable suture for gynecological and pediatric cases due to its predictable 90–120 day absorption and cost advantage over synthetic absorbables. A common bedside error is using plain catgut for subcuticular closure—it absorbs too rapidly (7–10 days), risking wound dehiscence; always specify chromic for delayed-absorption needs.

_Reference: Bailey & Love's Short Practice of Surgery, Ch. 6 (Surgical Materials & Sutures); KD Tripathi Essentials of Medical Pharmacology, Ch. 65 (Suture Materials)_