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J Feline Med Surg. 2025

Author

Obi Veterinary Education
February 11, 2026

Ultrasound-guided transversus abdominis plane block in obese cats: a preliminary cadaveric study

Marta Garbin 1,✉, Beatriz P Monteiro 1, Paulo V Steagall 1,2,3

Background
Effective perioperative analgesia in obese cats presents a clinical challenge due to increased adipose tissue, which can obscure anatomical landmarks and complicate locoregional anesthetic techniques. The transversus abdominis plane (TAP) block, used to desensitize the abdominal wall, has shown promise but lacks data in obese feline patients. This study aimed to characterize abdominal fat distribution in obese cats and assess whether injectate volume based on actual body weight (ABW) provides more extensive thoracolumbar nerve staining than that based on lean body weight (LBW).

Methods
This randomized, blinded, cadaveric descriptive study involved four cat cadavers with body condition scores ≥8/9. One cadaver was used for anatomical description; the other three underwent two-point ultrasound-guided TAP injections (subcostal and lateral-longitudinal) using bupivacaine-dye solution at volumes based on either LBW or ABW. Post-injection dissections were conducted to evaluate spread of injectate and circumferential staining (≥1 cm) of thoracolumbar spinal nerves from T10 to L2.

Results
Gross dissection revealed thick adipose layers between abdominal muscles, particularly between the rectus and transversus abdominis muscles cranially, and between the obliquus internus and transversus abdominis muscles caudolaterally. ABW-based volumes stained more spinal nerves (67%) than LBW-based volumes (50%), with ABW-based injections covering T11–L1 and LBW-based covering T12–L1. Ultrasound-guided injections were technically feasible but required greater time in obese cats due to adipose interference. No unintended dye spread into the abdominal cavity was observed.

Limitations
This was a small, preliminary cadaveric study using only four subjects, limiting generalizability. Functional efficacy and safety of the TAP block in live obese cats remains untested. Also, clinical outcomes such as analgesia duration and effectiveness were not assessed.

Conclusions
In obese cats, TAP blocks can be successfully performed using ultrasound guidance, though anatomical fat distribution complicates visualization. Anesthetic volumes based on ABW may enhance nerve staining, but safety considerations necessitate dose calculations based on LBW. These findings support further clinical trials to optimize locoregional analgesia protocols in this population.

Ultrasonographic identification of the transversus abdominis plane, abdominal muscles and adipose tissue in a cat cadaver with a body condition score of 9/9. (a) Schematic representation of the transducer positions in the cat in the dorsal position. The gray rectangles indicate the positions of the transducer, and the blue dot is the transducer marker (orientation). (b–d) Ultrasound images of the abdominal wall corresponding to the transducer in positions: (b), lateral–longitudinal to the mammary line and the level of the umbilicis; (c), close to the linea alba; and (d), subcostal at the level of the mammary line. Cd = caudal; Cr = cranial; D = dorsal; L = lateral; M = medial; OEA = obliquus externus abdominis muscle; OIA = obliquus internus abdominis muscle; RA = recus abdominis muscle; TA = transversus abdominis muscle; V = ventral

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