Cerebrospinal fluid changes after iopamidol and metrizamide myelography in clinically normal dogs

Cerebrospinal fluid samples from 2 groups of clinically normal dogs were compared after iopamidol (n = 9) and metrizamide (n = 8) myelography. Iopamidol (200 mg of I/ml) and metrizamide (170 mg of I/ml) were administered by cerebellomedullary injection at dosage of 0.45 ml/kg of body weight. In dogs of both groups, postmyelographic CSF changes included high specific gravity, Pandy score, protein concentration, and WBC count. The high specific gravity and Pandy score were false-positive effects attributed to nonionic contrast media. Although postmyelographic protein concentration and total WBC count were greater in CSF samples from dogs given metrizamide than in those given iopamidol, differences were not statistically significant. The differential WBC counts were consistent with mild, acute leptomeningitis; these findings were supported by results of histologic examination. Iopamidol and metrizamide should be considered low-grade leptomeningeal irritants in dogs.