A 12-year-old female spayed basset hound presented to DoveLewis Veterinary Emergency & Specialty Hospital with a history of vomiting, lethargy and multiple episodes of straining to urinate. Physical exam findings included a large, firm, right anal sac mass and suspected distention of the urinary bladder. The patient seemed painful on caudal abdominal palpation. A single lateral radiograph of the abdomen was performed.
The single lateral radiograph of the abdomen demonstrates a moderately to severely distended urinary bladder without evidence of a calculus. An additional view of the perineal region would be recommended to evaluate the entire urethra. No peritoneal or retroperitoneal effusion is present. There is an ovoid soft tissue opacity dorsal to the descending colon at the level of the fifth and sixth lumbar vertebra which measures 5 cm from ventral to dorsal and almost 8 cm from cranial to caudal (outlined with arrows). This mass appears to displace the colon ventrally. Abdominal sonography confirmed this to most likely reflect a severely enlarged medial iliac lymph node chain – most consistent with metastatic extension of anal sac neoplasia.
Partial urinary bladder obstruction secondary to dorsal compression was suspected and these lymph nodes involved the entire sublumbar chain into the pelvis. It was also possible that the large, firm, anal sac mass extended into the peritoneum and compressed the distal aspect of the urethra. A retrograde urethrogram may have been helpful to determine the location of urethral obstruction.
The patient was euthanized due to the severity of clinical signs and prognosis. The sublumbar chain of lymph nodes is bilateral and includes medial iliac, hypogastric and sacral lymph nodes from cranial to caudal. Normal medial iliac lymph node can be identified sonographically and typically measure less than 5 mm in height. Both reactive lymph node enlargement and neoplastic infiltration of lymph nodes should be considered given lymph node enlargement. However, lymph nodes greater than 2.5 cm in height most likely reflect a neoplastic process. Cytologic evaluation from 22-gauge fine-needle lymph node aspiration is necessary for definitive diagnosis