Catgut Sutures

Catgut/Surgical Gut Sutures

Gut sutures are the oldest natural absorbable multifilament sutures being used till the date. Commonly used gut suture is known as catgut which is derived from intestinal tissue of sheep / goat or Bovine (cattle). Catgut is mistaken to be manufactured from cat tissue due to its name as misnomer. Catgut word seems to be originated from Kitgut – fiddle string with kit being in the name of an Arabian fiddle with strings made from sheep intestine.


Catgut biothread is obtained from the submucosa of small intestine of ovine / sheep or serosal layer of bovine small intestine and is the most widely used absorbable suture material. It is the most widely used suture material in ruminant or large animal surgery.

Types of Catgut

Catgut is available in plain and chromatized form both. Catgut is categorized depending on the degree of chromatization.


Degree of chromatization

Loss of tensile strength

Absorption time

Type A


5 days

10 days

Type B

Mild chromic

10 days

15 days

Type C

Medium chromic

20 days

20 days

Type D


40 days

40 days

A. Plain Catgut / Fast Absorbing Gut Sutures

Processed collagen fibers from the gut serosa or mucosa are called fast absorbing surgical gut sutures. Slender strands of chemically treated highly purified collagen fibers are woven together to form a suture in wet condition. This process creates a strand of uniform diameter which is further polished to achieve maximum smoothness, for reliability and strength. It gives monofilament finish to the thread. Purity of collagen is important for optimal tensile strength and quality of the suture material. More purity or percentage of collagen fibers is responsible for superior tensile strength, lower tissue reactions and superior tensile strength. They lose tensile strength from 12 – 15 days usually.

plain Chromic Catgut Suture

Plain Catgut Suture (By Dolphin Sutures)

They incite more tissue reaction (more purified collagen may cause minimal tissue reaction); have unpredictable and rapid loss of tensile strength and absorption. Undyed plain catgut sutures are ivory in colour. Fast catgut sutures are heat treated to facilitate more rapid absorption in the body.

B. Chromic Catgut Suture

Catgut is composed of formaldehyde treated collagen fibers. The absorption time can be delayed by treatment of plain catgut with chromic acid, iodine, tannin, formalin, or other chemicals. Usually chromic acid is used along with oxidized pyrogallol to increase its tensile strength and absorption time and to decrease the tissue reaction. Absorption time may range from 90 to 120 days. It also gives chromic catgut dark brown colour. Collagen fibers are treated (not coated) with chromium salt prior to spin into suture strands. It is a multifilament suture with capillary action. It can be sterilized by distilled water and isopropyl alcohol, ionising radiation or by ethylene oxide, however, ethylene oxide prolongs absorption time of catgut.

absorbable Chromic Catgut Suture

Chromic Catgut Suture (By Dolphin Sutures)

Uniform treatment with chromium salt solution or chromatization of the catgut also makes surface more smooth and facilitates knot rundown and knot security.

Catgut sutures are marketed in the pre-sterilized aluminium foils containing 85% ethyl alcohol/ isopropyl alcohol with distilled water or in a solution of 89% isopropanol, 10% water and 1% triethanolmine / contains isopropanol, water, sodium benzoate and 0.40 -0.45% of ethylene oxide. Aluminium foils are further packed in a secondary paper pouch laminated with polyester laminated poly film. It is not suitable for autoclave sterilization because of its proteinaceous nature heat denatures the protein and it loses its original tensile strength. Packing material like IPA helps in retaining memory and increasing pliability.

Tissue Reaction

Due to heterogenic origin and proteinaceous nature of the catgut suture is also responsible for the grade 1 tissue reaction (slight or less with chromicised) and quick absorption or biodegradation. Allergic reaction or response may be limited to transient local irritation at the wound site or followed by moderate transient inflammatory foreign body response. 

Plain catgut thread / suture is not used routinely in surgery because it incites severe tissue reaction and rapid loss of tensile strength and absorption.

Absorption takes place by macrophages and lysosomal enzymes (phagocytosis). Mild to medium surgical guts routinely used.

Catgut Suture Sizes

The catgut is available in various sizes depending upon its diameter with needle – swaged or without needle. Needle may be 3/8 circle round body/circle cutting, ½ circle reverse cutting/circle round body ranging 16 mm to 55 mm length.  Suture length may vary from 76 cm to 152 cm. Double arm or single thread sometimes with heavy round body needle on thicker suture materials. Most of the manufacturer offers modification or customization according to need on bulk orders.

Catgut suture sizes / USP size varies from No. 7/0 (finest) to No. 4 (thickest).

Catgut suture sizes

Average Diameter (in mm)


2/0 – 3/0


Peritoneum, bowel wall of small animals and blood vessel ligature, Pedicles

0 or 1/0





Muscle fascia (small animals), ligature of larger vessels






Fascia, muscles of large animal






Rumen, uterus, abdomen

Knot Security

Catgut suture has good handling characteristics but in larger sizes show more suture memory and stiffness which becomes less ideal for knot security and handling. Catgut weakens, becomes soft, elastic material and swells in vivo after fluid absorption hence results in poor knot security so the cut ends of the sutures must be kept longer to avoid unravelling of knots. Minimum 3 throws are recommended to secure a knot generally in interrupted pattern while 4 throws for a starting knot and 5 throws for ending knots on continuous pattern. Cut ends should be long enough or 3-5 mm long to avoid unravelling of knots in the tissue after getting wet.

Tensile Strength

Though loss of tensile strength of any suture material depends on the type of material, tissue site and presence of infection but loss of tensile strength is unpredictable. Catgut suture loses its 33% tensile strength in 7 days and 67% in 28 days in general. Rapid loss of tensile strength can be seen in infected wounds, exposure to digestive enzymes in stomach or intestine, cervix, vagina, in highly vascular tissue and protein depleted or debilitated, malnourished, anaemic patients. It is absorbed faster in oral cavity, vagina, cervix or other mucus membranes due to presence of microorganisms. Catgut is economical but largely has been replaced by synthetic suture materials. Avoid crushing or crimping damage by forceps or needle holders during handling (handle needle in an area one third to one half of the distance from the attachment end to the point – handling from point may result into poor penetration or fracture and handling from butt may result into bending or breakage).

Pre-knotted loop ligature / loop chromic catgut sutures are also available.

Indications and Contraindications

Plain catgut sutures or fast absorbing gut suture should only be used for general closure like dermal / skin suturing or external knot tying only. Catgut / chromic catgut sutures are indicated for use in ophthalmic surgeries, orthopaedic surgeries, gynaecology/obstetrical surgeries, gastrointestinal tract surgeries, soft tissue / wound approximation / ligation, oral repairs, nail bed laceration repairs but not cardiovascular surgeries or neurological surgeries.

Catgut sutures should not be used in patients with a known history of sensitivity or allergy due to any of its components,  or where extended approximation is required or rapid loss of tensile strength is suspected as discussed above (should be avoided for laparotomy incision closure). According to the studies surgical gut suture may induce granuloma formation.  Malnourished or patients suffering from condition delay wound healing are not suitable for catgut sutures. Use in biliary or urinary tract may lead to calculus formation.

Use of supplemental non-absorbable sutures is recommended in the closure of sites which may go under expansion, stretching or distension or may require additional support.

Care should be taken while opening the package because it contains sterilizing fluids. It should not be re-sterilized and unused sutures must be discarded.

Catgut suture disadvantages: main disadvantage of using catgut suture is tissue reaction due to proteinaceous nature. It is more with plain catgut sutures in comparison to chromic catgut sutures.


Plain catgut : pale straw coloured / ivory coloured

Chromic catgut: Beige / dark brown colored

Storage: Should be stored in a cool and dry condition. And open or damaged package should not be used. Expired sutures should be discarded.

Note: Catgut sutures are banned in Japan and European union because of concern of spread zoonoses like bovine spongiform encephalopathy (BSE) or mad cow disease.


Catgut name is derived from the word kitgut or kitstring used for Arabian fiddle strings. It has nothing to be done with cat tissue or being originated from cat.

Yes. It is being used in ruminant surgery in animals and cat dogs too. But use in human practice is limited due to availability of the better synthetic absorbable suture material like vicryl, polyglycolic acid, polyglactin, polydioxanone etc.

In medical terms it means a tough cord made usually from the sheep or bovine intestines. It is used for surgical procedures. Catgut stitches are dissolvable and do not need removal.

No. No suture material is made from cat guts. Dissolvable stitches are mostly synthetic in nature in modern practice. Catgut is made from sheep or bovine intestines.

Catgut sutures (plain catgut sutures / surgical catgut or catgut strings) are harvested from intestines of sheep/goat or buffalo and further processed.

Catgut is used for surgical repairs or the tissues and ligatures. Use of animal intestine or gut is also have been popular for making of strings of the tennis rackets, archery bows, violin and other related instruments.

Catgut sutures are of two type mainly – plain catgut and chromic catgut. Catgut in general can be classified into 4 types depending on the degree of chromatization.

Yes. Chromic catgut sutures are types of dissolvable sutures. Time of absorption depends on the degree of chromatization and varies from 15 days to 40 days generally.

Catgut is treated with chromic acid to improve its tensile strength and reduce tissue reaction. It is called chromic catgut and has longer absorption time than plain catgut. It is important to note that they are treated with chromic acid not coated.

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