When A Mass Won't Resolve
Schmidt, a NM Boxer mix who is approximately 9 months old, was recently adopted. Four months after being adopted, Schmidt developed diarrhea that resolved with treatment, but his chemistry panel and CBC were suspicious for Valley Fever. However, two Valley Fever titers were negative. A painful mass then soon developed on his left side over his caudal ribs. Radiographs did not reveal anything significant, aside from the soft tissue mass, which was aspirated and revealed purulent material with rod bacteria in it. It was lanced, a drain was placed, and Schmidt was placed on appropriate antibiotics based on culture and sensitivity.
Despite medical management, the mass did not completely heal, so a couple of months later, the mass was explored further. A small, firm, and free-floating piece of material and purulent material were identified within the thick-walled mass. A deep tract was also identified that extended toward/into the intercostal spaces. Histopathology of the mass wall revealed changes consistent with an abscess and the material was suspected to be a bone sequestrum (not submitted for histopathology).
The mass persisted, and Schmidt was referred for consultation with DVMS' Internal Medicine department for additional diagnostics to help determine the underlying cause. Ultrasound was discussed, but inflammation often makes ultrasound imaging difficult since it is so indistinct and distorts adjacent normal tissues. It might also be difficult to completely evaluate the extent of disease via ultrasound due to shadowing from the ribs. Radiographs had already been performed and were not revealing, so a CT scan was elected because there is no shadowing from ribs and gas, there is no distortion from the inflammation, and CT eliminates superimposition from adjacent organs since it is a 3-dimensional imaging modality.
The CT scan revealed an approximately 17.5cm linear foreign body within the stomach that extended through the body wall and into the deepest part of the body wall mass (Figure 1).The mass did not penetrate into the abdomen and was visibly consistent with a chronic abscess. The foreign body also caused a reaction of the left thirteenth rib, resulting in thickening of the rib and a defect in the cranial aspect of the rib, as it passed by/through this rib (Figure 2). CT also revealed that there was no peritoneal effusion that might have indicated peritonitis and increased the time of surgery and difficulty of recovery.
Figure 1 (Left) Figure 2(Right)
Surgery was performed the same day and the foreign body and abscess were removed. Schmidt recovered uneventfully from surgery and is healing well at last recheck. In this case, as a diagnostic tool, CT was also extremely helpful to identify the source of the problem, confirm the character of the mass, and help the surgeon anticipate the possible surgical and recovery complications.