Dog Walks Again After Surgeons Remove Entire Lower Back Muscle Group to Excise Rare Spinal Tumor

In a veterinary first, surgeons at University College Dublin have reported the complete removal of an entire group of lower back muscles from a dog to treat a rare fatty tumor, and the patient made a full return to normal life. The case, published in the journal Veterinary Oncology, describes how a ten-year-old Border Collie lost the multifidus, longissimus lumborum, and iliocostalis lumborum muscles along the entire lumbar section of its spine, from the thirteenth thoracic vertebra to the seventh lumbar vertebra, and still walked, ran, and played normally sixteen months later. The report is believed to be the first documented account of functional outcomes following such an extensive resection of the epaxial musculature, the column of muscles that runs alongside the vertebral column and stabilizes the trunk during movement.

The patient arrived at the referral hospital with a large, firm, painless swelling on the left side of its lower back, just ahead of the hip. The mass measured fourteen by seven by seven centimeters on palpation, an imposing finding in a dog weighing just under twenty-three kilograms. The dog also carried a second diagnosis: hypoadrenocorticism, or Addison’s disease, a hormonal disorder that was already well controlled with medication. Blood tests showed markedly elevated liver enzymes and blood lipids, changes the team attributed to the corticosteroid treatment for the endocrine condition rather than to the mass itself.

Computed tomography settled the question of what the surgeons were dealing with. Contrast-enhanced scans revealed a well-defined mass embedded within the longissimus lumborum, the largest muscle of the epaxial group, stretching from the first to the sixth lumbar vertebra. The lesion was heterogeneous, composed mostly of fat attenuation but interspersed with soft tissue components that enhanced with contrast, along with a central area of soft tissue density surrounded by an enhancing rim and small peripheral mineral foci. Critically, the scan showed no bony destruction of the vertebrae and no evidence of metastatic spread to the chest or abdomen. Fine-needle aspiration cytology delivered the final piece of the puzzle: adipocytes, or fat cells, displaying extreme variation in nuclear size, karyomegaly, bizarre nuclear shapes, and abnormal nucleolar variation, a constellation of features consistent with liposarcoma.

Liposarcomas are uncommon malignant tumors in dogs, typically arising in the fat beneath the skin along the belly and limbs, and intramuscular examples involving the back muscles are exceedingly rare, with only three previous case reports describing their surgical management. Like other soft tissue sarcomas, they tend to invade locally rather than spread distantly, and the extent of surgical resection has been shown to dramatically influence survival. In the largest published series of canine liposarcomas, median survival reached 1,188 days after wide resection, compared with 649 days after marginal excision and just 183 days after incisional biopsy alone. That evidence placed enormous weight on the surgical plan, because the anatomy of the lumbar back would not permit a textbook wide excision.

The surgical team initially considered a compartmental excision, removing the entire anatomical unit of the affected muscle, an approach that has produced good outcomes for intramuscular sarcomas confined to a single muscle belly. Close study of the anatomy ruled it out. Dorsally and laterally, the thoracolumbar fascia forms a discrete fascial sheet, but medially and ventrally it inserts directly onto the spinous processes of the vertebrae and sends deep fascial extensions around the intertransversarii muscles, while the multifidus lies immediately adjacent to the longissimus with no distinct fascial boundary between them. The intimate attachment of the epaxial muscles to the lumbar vertebrae, anchored to the mamillary, spinous, accessory, and transverse processes, meant the entire compartment could not be removed without violating the spine itself. Microscopic tumor spread along these interfascial planes could not be excluded, so the team planned a marginal excision, removing the full muscle group en bloc while preserving the lumbodorsal fascia.

The operation itself was formidable. Working from the thirteenth thoracic vertebra caudally, the surgeons sharply incised the fascia on the midline and meticulously elevated the multifidus from its vertebral origins and insertions using periosteal elevators and diathermy, then freed the longissimus lumborum and iliocostalis from the accessory and transverse processes, from the twelfth and thirteenth ribs cranially, and from their insertions on the iliac crest caudally. The tumor remained grossly contained within the resected muscle and was never directly visualized. The principal hazard was hemorrhage from the lumbar spinal arterial branches as they exited each neuroforamen, vessels whose location within the bony openings of the spine made them difficult to control even with diathermy. Acute blood loss reached 340 milliliters, and the dog developed persistent hypotension, with mean arterial pressure falling below 60 millimeters of mercury for roughly an hour and dipping to 40 to 50 despite crystalloid and synthetic colloid fluid resuscitation. A transfusion of 300 milliliters of packed red blood cells normalized blood pressure within fifteen minutes, with no transfusion reactions.

Recovery brought its own challenges. For the first forty-eight hours the dog could not walk without support, showing marked weakness in the left hindlimb. Formal neurological examinations performed daily during hospitalization found no proprioceptive deficits or spinal nerve dysfunction, leading the team to attribute the weakness to a combination of postoperative pain, the sudden loss of extensive unilateral epaxial muscle function, and possibly transient neuropraxia of adjacent lumbar spinal nerves. The dog was walking unassisted within seventy-two hours. Pain management was aggressively multimodal, combining a morphine and bupivacaine epidural, intravenous paracetamol, a fentanyl infusion, ketamine, gabapentin, and a bupivacaine wound infusion catheter, all tapered as the patient improved. An active drain and the infusion catheter were removed on day four, and the dog went home on day five, comfortable and ambulatory.

Histopathology confirmed a well-differentiated liposarcoma, composed of round to polygonal cells in solid sheets with lipid-filled vacuoles and a mitotic count below one per 2.37 square millimeters, indicating a low-grade lesion. One important caveat emerged: neoplastic cells were present at the medial muscle margin, meaning excision was incomplete, although shave margins taken from the interspinalis, intertransversarii, and longissimus thoracis muscles and the medial ilium were all clear. Adjuvant radiotherapy and electrochemotherapy were discussed but unavailable in Ireland at the time, and the owners declined chemotherapy in favor of monitoring. The team notes that even incompletely excised low-to-intermediate grade soft tissue sarcomas do not always recur, with no recurrence reported in up to 66 percent of such cases, and that the absence of recurrence here likely reflects the tumor’s indolent biology rather than a complete excision.

The functional story is the most striking part of the report. At two weeks the dog was off all analgesia, but examination revealed a visible indentation of the left lumbar region with marked right-convex scoliosis, a compensatory curvature of the spine, plus mild persistent left hindlimb weakness with occasional scuffing and stumbling. Normal exercise resumed at eight weeks, though the owner still noticed intermittent stumbling during running or standing up to six months after surgery. By long-term follow-up, assessed through owner reports, orthopedic examination by the referring veterinarian, and video gait analysis, the dog had returned to normal activity with no evident lameness or weakness, the scoliosis had improved, and no long-term pain relief or physical therapy was needed. No gross recurrence was detected on physical examination at sixteen months, and the owner said they would make the same treatment decision again.

The authors caution that a single case cannot settle every question. The epaxial muscles contribute to propulsion and dynamically stabilize the trunk against gravitational and inertial forces, and in greyhounds the longissimus dorsi and iliocostalis lumborum are estimated to augment hindlimb muscle power by roughly twelve percent, so the consequences of removing them remain incompletely understood. Objective kinematic gait analysis, force plate measurements, validated clinical metrology instruments, and advanced imaging would be needed to detect subtle degenerative or compensatory changes in the vertebral column, and the absence of follow-up imaging is a key limitation, since recurrence surveillance relied on physical examination alone. Still, the message for veterinary surgeons is concrete: extensive unilateral lumbar epaxial muscle resection can carry acceptable perioperative morbidity and deliver an excellent long-term quality of life, provided teams anticipate substantial blood loss, prepare for transfusion, and counsel owners about a recovery that demands patience before it rewards it.

Subject of Research: Extensive epaxial muscle resection for treatment of a lumbar liposarcoma in a dog

Article Title: Long-term clinical and functional outcome following extensive left-sided epaxial muscle resection (T13-L7) for a longissimus lumborum liposarcoma in a dog – case report

Article References: Long-term clinical and functional outcome following extensive left-sided epaxial muscle resection (T13-L7) for a longissimus lumborum liposarcoma in a dog – case report. (n.d.). https://doi.org/10.1186/s44356-026-00079-y

Image Credits: AI Generated

DOI: 10.1186/s44356-026-00079-y

Keywords: liposarcoma, epaxial muscle, veterinary oncology, soft tissue sarcoma, dog, marginal excision, spinal stabilization, computed tomography, surgical margins, Border Collie, scoliosis, case report