Treatment and follow-up
Because of the deep retroperitoneal location of the foreign body and its proximity to the aorta, an exploratory celiotomy
was performed. The foreign body's location was not evident on gross inspection of the abdomen during initial exploration.
Intraoperative ultrasonography was used to localize the foreign body within the hypaxial musculature. An incision was made
into the retroperitoneal space, and the ureter and aorta were preserved. A 3-cm incision was made in the musculature over
the suspected foreign body, and a 6-cm stick was removed intact (Figures 4 & 5). Samples of the tissue surrounding the foreign body were submitted for fungal and bacterial culture.
Figure 4. An intraoperative photograph of the foreign body deep in the retroperitoneal space in the hypaxial musculature.
The retroperitoneum and abdominal cavity were lavaged copiously with saline solution. No attempt was made to remove the draining
tracts. Intravenous enrofloxacin (one dose; 21 mg/kg) was administered. Omentum was placed over the foreign body site and
tacked into place by using simple interrupted sutures using 4-0 poliglecaprone 25 suture. The linea alba was closed in a simple
continuous pattern with 0 polydioxanone suture. The subcutaneous tissue was closed in a simple continuous pattern with 3-0
polydioxanone suture. The skin was closed with surgical staples.
Figure 5. The foreign body, a stick, measured 6 cm.
After surgery, the flank abscess appeared to communicate with the retroperitoneal draining tract because there was a large
amount of caseous, mucopurulent discharge and lavage fluids exiting the flank sinus. Postoperative topical cleansing was performed
on an as-needed basis with 4-in-x-4-in gauze and a dilute chlorhexidine solution. Sulfamethoxazole-trimethoprim (66 mg/kg
and 13 mg/kg orally b.i.d.) and amoxicillin (22 mg/kg orally t.i.d.) were instituted after surgery, pending culture and antimicrobial
sensitivity testing. A Schirmer tear test, performed before sulfamethoxazole-trimethoprim therapy was instituted, revealed
normal tear function in both eyes.
Bacterial culture and antimicrobial sensitivity testing results indicated a mixed population of a few diphtheroid bacteria,
an undetermined amount of gram-negative anaerobic rods, and an undetermined number of gram-positive anaerobic cocci. Bacteria
could not be isolated and identified from culture. The culture results for mycoplasma and fungi were negative.
By two days after surgery, the skin tracts had sealed (Figure 6). The dog was then discharged, and antimicrobial therapy was continued as prescribed postoperatively for a total of 28 days.
Eleven months after presentation, the owner reported that the dog was doing well. There had been no drainage or swelling in
the flank, and the dog's body condition had returned to normal.
Figure 6. The patient two days after recovery from surgery. Inset: A close-up of the dog's left flank. The drainage has stopped,
and the cutaneous tracts have started to heal.
Differential diagnoses for chronic draining tracts include infection with pyogenic organisms, a foreign body nidus, bone sequestra,
neoplasia, fungal infections, and osteomyelitis.1,2 Because chronic microbial infection is associated with or a direct cause of chronic draining tracts, it stands to reason
that chronic draining tracts may be complicated or perpetuated by immune-mediated disease and concurrent immune suppression
(hyperadrenocorticism, immunosuppressive therapy, or other concurrent systemic disease that has exhausted the immune system).
Abscess formation that is nonresponsive or is initially responsive but relapses after treatment is discontinued should alert
the clinician to the presence of one or more of the above pathologic processes.