Introduction
A 4-month-old 17.5-kg neutered male Boxer was referred to the neurology department of a referral veterinary hospital for evaluation of a 3-day history of acute-onset progressive reluctance to walk, right pelvic limb lameness progressing to non–weight-bearing lameness, and spontaneous yelping when standing up and walking, with no history of trauma. Radiographic findings for the lumbosacral region, pelvis, and hip and knee joints were unremarkable (Figure 1). Prior to referral, the dog received meloxicam, which lead to mild improvement; however, on the day before referral, the dog’s condition deteriorated.
Ventrodorsal (A) and lateral (B) radiographic images of the sacroiliac joints in a 4-month-old Boxer with a 3-day history of acute-onset progressive reluctance to walk, right pelvic limb lameness progressing to non–weight-bearing lameness, and spontaneous yelping when standing up and walking. There was no history of trauma.
Citation: Journal of the American Veterinary Medical Association 260, 8; 10.2460/javma.20.10.0581
Ventrodorsal (A) and lateral (B) radiographic images of the sacroiliac joints in a 4-month-old Boxer with a 3-day history of acute-onset progressive reluctance to walk, right pelvic limb lameness progressing to non–weight-bearing lameness, and spontaneous yelping when standing up and walking. There was no history of trauma.
Citation: Journal of the American Veterinary Medical Association 260, 8; 10.2460/javma.20.10.0581
Ventrodorsal (A) and lateral (B) radiographic images of the sacroiliac joints in a 4-month-old Boxer with a 3-day history of acute-onset progressive reluctance to walk, right pelvic limb lameness progressing to non–weight-bearing lameness, and spontaneous yelping when standing up and walking. There was no history of trauma.
Citation: Journal of the American Veterinary Medical Association 260, 8; 10.2460/javma.20.10.0581
On presentation, the dog was ambulatory with non–weight-bearing lameness of the right pelvic limb. Any attempt to stand up or walk resulted in severe yelping. Physical examination revealed rectal temperature of 39.2 °C, heart rate of 180 beats/min with strong femoral pulses, and respiratory rate of 36 breaths/min. Results of an orthopedic examination were unremarkable except for consistent hyperesthesia during extension of the hip joints bilaterally. Neurologic examination revealed a severe non–weight-bearing lameness of the right pelvic limb, mild inconsistently delayed postural reactions on both pelvic limbs, and a reduced right pelvic limb withdrawal reflex.
Assessment
Anatomic diagnosis
The non–weight-bearing right pelvic limb lameness and spontaneous yelping on standing or walking were considered to most likely be a result of an orthopedic condition (eg, cruciate ligament disease, hip dysplasia, a fracture, or panosteitis), septic arthritis, or a myopathy (eg, abscess, foreign body, compartment syndrome, or neoplasia). In addition, the spontaneous yelping episodes could have been a result of nonspecific spinal disease (eg, an infectious process of the vertebrae such as diskospondylitis, physitis, or osteomyelitis or neoplasia). The mild ambulatory paraparesis without ataxia but with a reduced withdrawal reflex of the right pelvic limb was most likely a result of a lesion involving the L6-S1 spinal cord segments or associated nerve roots on the right side.
Likely location of a single lesion
The most likely location of a single lesion was the L6-S1 spinal cord segments or associated nerve roots on the right side.
Etiologic diagnosis
Primary differential diagnoses included inflammatory and infectious processes involving bone or the intervertebral disks, joints, or nerves (eg, neosporosis, toxoplasmosis, or brucellosis, with ehrlichiosis, anaplasmosis, and borreliosis considered much less likely because these conditions were not endemic) and neoplasia directly affecting the bone, joints, or nerves (eg, nerve sheath tumor, meningioma, or a primary bone tumor) or within the vertebral column (eg, lymphoma). Intervertebral disk disease was not considered likely owing to the animal’s young age.
Diagnostic Plan
The diagnostic plan included a CBC and serum biochemical profile including C-reactive protein concentration, cross-sectional CT of the entire body, and MRI of the lumbosacral vertebral column and both lumbosacral plexuses. Serologic assessment for antibodies against infectious agents, antimicrobial culture, lumbar CSF analysis, and electrodiagnostic testing were to be considered in light of the results of the initial diagnostic testing.
Diagnostic Test Findings
Results of a CBC and serum biochemistry profile were unremarkable, but the C-reactive protein concentration was high (74.11 mg/L; reference range, < 10 mg/L). The dog was anesthetized, full-body CT without contrast was performed with a helical, multidetector, 16-slice system (Somatom Sensation; Siemens Medical GmbH), and MRI of the lumbosacral region was performed with a low-field 0.25 T permanent magnet (Vet-MR Grande; Esaote). Magnetic resonance imaging sequences included sagittal and transverse T2-weighted (T2W) images, dorsal and transverse STIR images, and transverse T1-weighted images before and after contrast administration.
Computed tomography revealed faint, multifocal, aggressive lesions centered at the right sacroiliac joint and affecting the sacral tuberosity of the right ilium and adjacent lateral aspect of the sacrum. These lesions were characterized by ill-defined hypoattenuating areas and partial cortical disruption. No surrounding sclerosis or irregular periosteal proliferation was noted (Figure 2), and no soft tissue abnormalities were seen.
Dorsal-plane (A) and transverse-plane (B) CT images of the sacroiliac joints in the dog in Figure 1. Notice the faint, multifocal, aggressive lesions (arrows) affecting the sacral tuberosity of the right ilium and adjacent lateral aspect of the sacrum and causing partial cortical disruption.
Citation: Journal of the American Veterinary Medical Association 260, 8; 10.2460/javma.20.10.0581
Dorsal-plane (A) and transverse-plane (B) CT images of the sacroiliac joints in the dog in Figure 1. Notice the faint, multifocal, aggressive lesions (arrows) affecting the sacral tuberosity of the right ilium and adjacent lateral aspect of the sacrum and causing partial cortical disruption.
Citation: Journal of the American Veterinary Medical Association 260, 8; 10.2460/javma.20.10.0581
Dorsal-plane (A) and transverse-plane (B) CT images of the sacroiliac joints in the dog in Figure 1. Notice the faint, multifocal, aggressive lesions (arrows) affecting the sacral tuberosity of the right ilium and adjacent lateral aspect of the sacrum and causing partial cortical disruption.
Citation: Journal of the American Veterinary Medical Association 260, 8; 10.2460/javma.20.10.0581
Magnetic resonance imaging highlighted the aggressive character of the right sacroiliac lesion as an ill-defined lesion affecting the cortex and medulla of the ilium and sacrum. The lesion was hyperintense on T2W and STIR images, compared with the spinal cord, and hypointense on T1-weighted images and had moderate and rather homogeneous contrast enhancement (Figure 3). The adjacent right gluteal muscles and right dorsal epaxial muscles were also affected, with a similar signal intensity pattern as described for the bone lesions.
Transverse-plane T2-weighted (A), STIR (B), T1-weighted (T1W) precontrast (C), and T1W postcontrast (D) images and dorsal-plane STIR (E) and T1W postcontrast (F) MRI images of the sacroiliac joints of the dog in Figure 1. Notice the ill-defined lesion affecting the cortex and medulla of the ilium and sacrum; the lesion is hyperintense on T2-weighted and STIR images and hypointense on T1W images and has moderate homogeneous contrast enhancement. The adjacent right gluteal and right dorsal epaxial muscles were also affected.
Citation: Journal of the American Veterinary Medical Association 260, 8; 10.2460/javma.20.10.0581
Transverse-plane T2-weighted (A), STIR (B), T1-weighted (T1W) precontrast (C), and T1W postcontrast (D) images and dorsal-plane STIR (E) and T1W postcontrast (F) MRI images of the sacroiliac joints of the dog in Figure 1. Notice the ill-defined lesion affecting the cortex and medulla of the ilium and sacrum; the lesion is hyperintense on T2-weighted and STIR images and hypointense on T1W images and has moderate homogeneous contrast enhancement. The adjacent right gluteal and right dorsal epaxial muscles were also affected.
Citation: Journal of the American Veterinary Medical Association 260, 8; 10.2460/javma.20.10.0581
Transverse-plane T2-weighted (A), STIR (B), T1-weighted (T1W) precontrast (C), and T1W postcontrast (D) images and dorsal-plane STIR (E) and T1W postcontrast (F) MRI images of the sacroiliac joints of the dog in Figure 1. Notice the ill-defined lesion affecting the cortex and medulla of the ilium and sacrum; the lesion is hyperintense on T2-weighted and STIR images and hypointense on T1W images and has moderate homogeneous contrast enhancement. The adjacent right gluteal and right dorsal epaxial muscles were also affected.
Citation: Journal of the American Veterinary Medical Association 260, 8; 10.2460/javma.20.10.0581
A CT-guided fine-needle aspirate was obtained from the right sacroiliac joint. Results of cytologic examination of the specimen were inconclusive, with no evidence of microorganisms. A CSF sample was not collected. Results of bacterial culture of blood samples from 2 peripheral veins, a sterilely collected urine sample, and the lesion fine-needle aspirate were all negative. Results of serologic testing for antibodies against Toxoplasma spp, Neospora spp, and Brucella canis were negative.
Treatment
On the basis of the dog’s clinical signs, laboratory testing results, and advanced imaging findings, infectious sacroiliitis was considered the primary differential diagnosis, even in the absence of positive bacterial culture results. The dog was treated with amoxicillin–clavulanic acid (20 mg/kg, IV, q 8 h) while results of serologic testing and bacterial culture were pending, and methadone (0.3 mg/kg, IV, q 4 h), meloxicam (0.1 mg/kg, PO, q 24 h), and gabapentin (11.43 mg/kg, PO, q 8 h) were prescribed for pain relief. After 24 hours of hospitalization, the dog was able to stand and walk without yelping despite occasional non–weight-bearing lameness of the right pelvic limb. The dog was discharged, and the owners were instructed to continue treatment with amoxicillin–clavulanic acid for 9 weeks in total, administer meloxicam for 10 days in total, and gradually taper the dosage of gabapentin over the next month.
The owner reported that the dog was back to almost-normal puppy-like behavior by day 4 of treatment. At a recheck examination 12 weeks after the onset of clinical signs and 3 weeks after administration of amoxicillin–clavulanic acid was discontinued, the dog was clinically normal, and results of neurologic and orthopedic examinations were unremarkable. Repeated imaging was not performed owing to monetary constraints and clinical resolution of signs.
Comments
Sacroiliitis refers to inflammation of the sacroiliac joint.1,2 The sacroiliac joint is an almost immobile joint (synchondrosis), firmly uniting the ilium and sacrum, and possesses both synovial and fibrocartilaginous components.3 This joint plays a pivotal role in weight-bearing and transmission of propulsion from the pelvic limbs to the spine during locomotion.4 Pathologic lesions affecting this joint have been long recognized in adults and children, including inflammatory noninfectious, infectious, neoplastic, traumatic, and degenerative conditions, with compromise of the sacroiliac joint being recognized as a contributing factor to low back pain syndrome in humans.5 In dogs, traumatic separation, fractures, and subluxation of the sacroiliac joints are commonly recognized and treated; however, information regarding degenerative changes of the sacroiliac joint is still limited.6,7 Degenerative canine sacroiliac joint disease, termed ankylosis capsularis ossea and sometimes referred to as pelvic ring anomaly,8 has the potential of contributing to lower back pain, sometimes accompanied by pelvic limb dysfunction, in dogs and can be clinically indistinguishable from other conditions affecting this region, such as degenerative lumbosacral stenosis and hip dysplasia.7,8 In people, inflammation at the level of the sacroiliac joint can develop as a result of infectious and noninfectious processes, with infectious lesions commonly related to tuberculosis or brucellosis in adults. When not caused by these pathogens, infectious sacroiliitis is considered rare in people and most commonly develops secondary to bacterial infection, although instances of fungal infection have been reported.2,9 Correctly differentiating the cause of sacroiliitis is vital in choosing the appropriate treatment and preventing deterioration or sepsis.
Infectious sacroiliitis is considered a rare condition in dogs, with only 3 dogs having been recognized with the condition, all of which were located in North America.1,10 In those 3 dogs, the diagnosis was made on the basis of results of diagnostic imaging (radiography, CT, and MRI) and positive bacterial culture results for blood, urine, or fine-needle aspirates. When results of bacterial culture were negative, a clinical response to antimicrobial treatment was considered supportive of the diagnosis.1,10
Clinically, infectious sacroiliitis seems to be almost indistinguishable from other processes causing lower back pain in dogs, such as degenerative lumbosacral stenosis, diskospondylitis, and hip dysplasia, and the diagnosis is one of exclusion on the basis of imaging findings. Reported clinical presentations include difficulty rising, reluctance to jump or walk, pelvic limb tremors, unilateral pelvic limb lameness sometimes accompanied by mild proprioceptive deficits of the affected and contralateral limbs, and a consistent painful response on lumbosacral palpation or tail or hip joint manipulation. Cases reported involved young, large-breed dogs with reported ages of 4 months (2 cases, including the dog described in the present report), 1.5 years, and 11 years, and reported breeds being Boxer (2 cases, including the dog described in the present report), Labrador Retriever, and Golden Retriever. Concomitant with infectious sacroiliitis, 1 dog also reportedly had diskospondylitis.10 Bacteria found to be implicated on the basis of positive culture results or an indirect fluorescent antibody screening test were Pasteurella canis (1 case) and B canis (1 case).1,10 The presentation in our case closely resembled pyogenic sacroiliitis in infants,11 which is typically not associated with invasive complications and for which the mild clinical course and fast recovery differ from findings for classic septic sacroiliitis in people.
Making a diagnosis of infectious sacroiliitis on the basis of diagnostic imaging findings can be challenging, particularly when radiography is the only modality used. Radiography can reveal changes in the sacroiliac joint indicative of sacroiliitis; however, an absence of radiographic changes does not rule out the diagnosis.1 Similar to what has been reported for diskospondylitis in dogs, radiography seems to fail to reveal early changes in and around the joint that can be detected by cross-sectional imaging modalities.1,12 Computed tomography has the potential to detect sacroiliitis earlier in its development, compared with radiography, providing greater detail in terms of bone demineralization and joint space changes, but is less accurate than MRI when assessing intra-articular and surrounding soft tissues.1
Computed tomographic features previously reported for a dog with infectious sacroiliitis were widening of the sacroiliac articulations with adjacent regions of subchondral sclerosis and regions of decreased cortical delineation adjacent to the sacroiliac articulations.10 In our case, there were irregular, poorly defined, hypoattenuating lesions of the sacral tuberosity of the right ilium, but the sacroiliac joint appeared to be of normal size and intensity and no changes in the surrounding soft tissue were evident. The lack of widening of the sacroiliac joint in our case could have been related to an earlier stage of the condition.
Magnetic resonance imaging is the gold standard in identifying infectious sacroiliitis in people and seems to have the same potential role in dogs.1,2 Reported MRI features of infectious sacroiliitis in dogs include increased T2W and STIR signal intensity of the sacroiliac joint alongside high STIR signal intensity of the sacroiliac periarticular musculature. Patchy multifocal contrast uptake has been reported in several structures, including the fibrocartilaginous portions of the sacroiliac joint, periarticular musculature, medullary cavity, iliac wing and body, and sacrum. A widened and irregular margination of the sacroiliac joint space with increased joint fluid was also previously described.1,10 Three of 4 reported cases involving dogs had unilateral imaging abnormalities, which is similar to reports in the human medicine literature,2,9 in which most infectious sacroiliitis cases are unilateral.
Evidence of high blood inflammatory markers, such as WBC count and serum C-reactive protein concentration, can aid in the detection of an underlying inflammatory infectious process but lack specificity. A high serum concentration of C-reactive protein, an acute phase protein particularly involved in early-stage injury and inflammation, was found in our case in accordance with reported findings in children with pyogenic sacroiliitis.11
Treatment of infectious sacroiliitis involves broad-spectrum antimicrobial treatment, ideally based on bacterial culture and susceptibility testing results.1,10 Antimicrobials that have been successfully used include amoxicillin–clavulanic acid, clindamycin, enrofloxacin, metronidazole, and sulfadimethoxine. In our case, we chose amoxicillin–clavulanic acid on the basis of its activity against gram-positive and gram-negative aerobic organisms, including P canis, which was identified in a previous case, and Escherichia coli, Staphylococcus spp, and Streptococcus spp, which are frequently isolated from dogs with diskospondylitis.13 In our case, results of bacterial culture of blood, urine, and fine-needle aspirate samples were negative. This was not surprising considering the fairly high prevalence of negative bacterial culture results (40% to 75% of cases) in dogs with diskospondylitis.13 This is also the case in pyogenic sacroiliitis in infants, in whom a bacterial source is not commonly identified.11
The outcome was favorable in our case and in previously reported cases of infectious sacroiliitis, with clinical resolution after 2, 6, or 9 weeks of antimicrobial treatment. In a study11 of infants with pyogenic sacroiliitis, the mean duration of antimicrobial treatment was 33.9 days and long-term follow-up did not reveal any recurrences. Recurrence of infectious sacroiliitis in dogs has not been reported as of yet; however, follow-up times were only 4 and 6 months in 2 cases and only 12 weeks in the present case.
In conclusion, infectious sacroiliitis appears to be a rare condition in dogs. The diagnosis can be made by excluding other conditions, and the prognosis appears to be excellent with appropriate antimicrobial treatment. This condition should be considered as a differential diagnosis in dogs presenting with apparent lower back pain and pelvic limb lameness.
References
- 1. ↑
Slater R, zur Linden A, James F. Diagnostic imaging characteristics of canine infectious sacroiliitis. Can Vet J. 2019;60(6):630–636.
- 2. ↑
Hermet M, Minichiello E, Flipo RM, et al. Infectious sacroiliitis: a retrospective, multicentre study of 39 adults. BMC Infect Dis. 2012;12:305. doi:10.1186/1471-2334-12-305
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Lavi E, Gileles-Hillel A, Simanovsky N, Averbuch D, Wexler ID, Berkun Y. Pyogenic sacroiliitis in children: don’t forget the very young. Eur J Pediatr. 2019;178(4):575–579.
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