Septic arthritis remains a common orthopaedic condition in both human and veterinary medicine which can cause serious morbidity and pose considerable challenges for clinical management. The majority of the published clinical research in humans and veterinary species has been focused on the diagnosis, treatment, prevention and outcome of this condition, with less emphasis on the direct sequelae of this condition, especially regarding its effects on the local bone. Osteomyelitis and osteonecrosis are often discussed as separate entities, but it can be argued that there are numerous similarities between the conditions and they can co-exist in clinical cases. The coexistence of these conditions has also likely been overlooked historically in part due to the difficulties in diagnosis. The evolution and adaptation of new diagnostic techniques available for the horse have and will continue to enable a more sensitive and specific appreciation of the pathologic lesions affecting tissues within and adjacent to the joint. The detection of these lesions provides new insights into the complex considerations in the management of septic arthritis and its bony sequelae.
Injury resulting in proliferative new bone formation on the dorsal aspect of the middle phalanx (P2) has been recognised by equine veterinarians and is generally referred to as capsulitis. However, no retrospective case series has been published on the condition.
To describe the clinical features, treatment, and outcome of this condition.
Case series (n = 19).
Clinical cases in which the horse presented for lameness and was diagnosed with acute formation of proliferative bone on the dorsal P2 diaphysis were included in the study (cases collected from 2005 to 2022). Signalment, history, presenting clinical signs, diagnostics, treatments administered, and outcome were evaluated.
Horses presented with unilateral lameness and were all classified as either a moderate lameness at a trot (n = 6) or a moderate to severe lameness at a walk (n = 13). A forelimb was involved in 79% of cases and a hindlimb in 21%. The presentation of lameness was recorded as acute in 15/19 horses and not reported in the remainder. Bone proliferation on the dorsal aspect of P2 was diagnosed on radiographic evaluation in all horses (as part of the inclusion criteria). In horses with sequential radiographs made from the time of acute presentation, bone production developed rapidly over a period of a few weeks to 2 months. A variety of therapeutic options were implemented, and 13/19 (68%) of the cases were subject to humane euthanasia, with only one horse returning to its previous athletic function. Milder cases were more likely to have a better outcome.
Small sample size and incomplete medical records.
Acute new bone proliferation on the dorsal aspect of P2 is associated with moderate to severe lameness and carries a poor prognosis for return to athletic function and survival.
A recently castrated 4-year-old Selle Français gelding was presented for evaluation of renal failure. Abdominal and transrectal ultrasonography revealed a large volume of anechoic free fluid in the peritoneal cavity, with a high creatinine concentration and a tear at the cranial pole of the bladder. Medical management was initiated for 2 days, followed by a standing laparoscopy to close the bladder wall defect using barbed sutures. The barbed sutures facilitated the procedure and reduced operative time, with no complications related to the suture technique. After a transient acute renal injury, the horse recovered and was discharged from the hospital 13 days postoperatively. To our knowledge, this case represents the first report of in vivo surgery using barbed sutures on an equine bladder.
A Shetland pony mare presented for investigation of colic of 6 h duration. On examination, she was tachycardic with moderate abdominal pain. Initial abdominal ultrasonography showed a large volume of swirling echogenic free fluid within the peritoneal cavity, which was confirmed to be sanguinous on abdominocentesis. Blood analysis showed a reduced haematocrit (14%), hypoproteinaemia (36 g/L) and increased lactate in addition to other mild abnormalities. She received a blood transfusion, and her haematological and biochemical parameters and comfort improved during her stay at the clinic. Repeat abdominal ultrasonography identified a large mass in the right side of the abdomen, adjacent to the right kidney, right dorsal colon, duodenum and right liver lobe. Computed tomographic examination of the abdomen performed under general anaesthesia confirmed this mass to be the markedly enlarged pancreas with cystic regions within it, and small gas foci within one of the cystic areas, consistent with abscessated pancreatitis. Ultrasound-guided biopsy of the mass was performed, and histopathology showed chronic suppurative and fibrosing pancreatitis. On further serum biochemical analysis, amylase activity was normal, but lipase was increased (30 u/L). The mare received a prolonged, tapering course of oral prednisolone. The pancreas could not be identified on repeat abdominal ultrasound 30 months post-initial presentation, and serial serum biochemical analysis has shown the lipase concentration to have reduced to normal limits. The mare remains systemically well at 4 years post-presentation. Equine pancreatic pathology is rare, with few reports of pancreatitis, pancreatic neoplasia and involvement in systemic disease processes. To the authors' knowledge, this is the first report on the use of CT and CT angiography to aid the diagnosis of equine pancreatitis, and the case highlights the utility of CT in the investigation of abdominal disease in small equine patients.
Neoplasia is rare in horses and central nervous system (CNS) neoplasia is so rare that, pituitary adenomas excluded, no specific intracranial neoplasms are mentioned in Cotchin's preliminary work describing the epidemiology of equine neoplasia (Cotchin, 1977). Moreover, an early survey identified 28 nervous tissue tumours in horses but none were reported in the central nervous system (Hayes Jr. et al., 1975). However, as de Sousa et al. (2025) highlight in the accompanying case report, equine intracranial neoplasia can cause significant clinical disease and histopathology is essential to making a complete diagnosis, albeit inevitably through post-mortem examination. Herein follows a brief discussion of a variety of intracranial tumours reported in horses and their histopathological diagnostic features with a summary of their immunohistochemical (IHC) characteristics in Table 1. Non-neoplastic causes of intracranial space-occupying lesions, for example, cholesterol granulomas, must always remain on the list of differential diagnoses but lie outside the remit of this commentary. Any readers seeking further details and descriptions of the characteristics of these lesions are encouraged to pursue some of the references at the end of this commentary, or indeed the associated case report.
There are a variety of reported intracranial neoplasms despite them remaining a rare diagnosis that relies on post-mortem examination. While the majority of types of tumours only exert clinical effects through a local mass effect, acting as benign space-occupying lesions, some neoplasms are malignant and the most common presentation of intracranial neoplasia remains PPID. The authors hope readers can better appreciate the heterogeneity of intracranial neoplasia and take home a greater understanding of how histological patterns allow pathologists to distinguish between grossly very similar masses.
H. G. Miller: Conceptualization; writing – original draft; writing – review and editing. A. Suarez-Bonnet: Conceptualization; writing – original draft; writing – review and editing.
There are no funders to report for this submission.
No conflicts of interest have been declared.
Not required for this clinical commentary.
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