Computed tomography of testicular torsion in a juvenile dog with unilateral cryptorchidism

Abstract

A 14-week-old male unilaterally cryptorchid Clumber spaniel was presented for acute lethargy. Physical examination revealed abdominal pain, and a single testis was palpated in the scrotum. Abdominal ultrasound and computed tomography (CT) revealed a poorly vascularized, ovoid structure immediately caudal to the left kidney with scant regional peritoneal effusion. Left intra-abdominal testicular torsion was confirmed at surgery, and routine cryptorchidectomy was performed. The patient recovered uneventfully from anesthesia and surgery.

Key clinical message:

The most common CT characteristics of testicular torsion were present in this case and correlated well with sonographic findings to allow for rapid, accurate diagnosis and surgical planning of unilateral, non-neoplastic, intra-abdominal cryptorchid testicular torsion in a juvenile dog. Contrast enhanced CT facilitated accurate localization of the undescended testis and evaluation of testicular perfusion and may be a useful alternative to ultrasound for diagnosing testicular torsion, especially in indeterminate cases.

Testicular torsion is rare in dogs and typically diagnosed by abdominal ultrasound; however, ultrasound may be indeterminate in some cases and further investigation may be required for definitive diagnosis. This report describes the computed tomographic (CT) features of non-neoplastic cryptorchid testicular torsion in a juvenile dog, which have not previously been reported. The increased availability and accessibility of CT in veterinary hospitals necessitates the description of CT findings to facilitate early disease recognition and efficient treatment in canine patients.

Case description

A 14-week-old, 11.9 kg intact male Clumber spaniel was presented for evaluation of acute lethargy following referral from the primary veterinarian. The morning before presentation, the puppy was noted to eat less enthusiastically than normal. No change in urination or defecation was noted, and there was no history of vomiting or diarrhea. Unilateral cryptorchidism had been previously diagnosed. Four subcutaneous injections of human chorionic gonadotropin (hCG; unknown dose) were given by the referring veterinarian to encourage testicular descent, with the most recent injection administered 4 d prior to presentation. On physical examination, the patient was quiet, alert, afebrile (38.6°C), and painful on abdominal palpation. A single testis was palpated in the scrotum.

A complete blood (cell) count (CBC) revealed a mild non-regenerative anemia with anisocytosis and macrocytosis, and a mild inflammatory leukogram characterized by leukocytosis, mature neutrophilia, and monocytosis. Serum biochemical analysis was normal for a juvenile patient, with mild hypokalemia, hyperphosphatemia, and elevated alkaline phosphatase (Table 1).

Table 1.

Hematological and biochemical abnormalities, including reference intervals.

Parameter	Value	Reference interval
RBC (× 106/μL)	4.40	5.60 to 8.40
HCT (%)	32	39 to 57
PCV (%)	31	40 to 59
WBC (× 103/μL)	19.1	5 to 14
Segmented neutrophils (× 103/μL)	14.3	2.6 to 10
Monocytes (× 103/μL)	1.9	0.1 to 0.9
Potassium (mmol/L)	3.7	3.9 to 5.3
Phosphorus (mg/dL)	8.7	2.2 to 7.9
ALP (U/L)	301	20 to 157

RBC — Red blood cells; HCT — Hematocrit; PCV — Packed cell volume; WBC — White blood cells; ALP — Alkaline phosphatase.

Abdominal radiographs performed by the referring veterinarian prior to presentation revealed gastrointestinal material consistent with a recent meal and no evidence of mechanical obstruction or other abnormalities (Figure 1). Abdominal ultrasound was performed using a 9-MHz, linear-array transducer (GE Logitech E9; GE Medical Systems, Milwaukee, Wisconsin, USA). The undescended left testis identified caudal to the left kidney was enlarged (1.84 × 2.48 cm), rounded, hyperechoic, and mildly heterogeneous, with a thin, linear central hyperechoic line (mediastinum testis) (Figure 2). The severely enlarged left epididymis and spermatic cord (1.20-cm thick) were hypoechoic with a tortuous path that abruptly tapered and could not be followed caudally. Color and power Doppler interrogation revealed minimal flow signal on the peripheral aspects of the left spermatic cord, and no identified flow signal within the left testis. The mesentery adjacent to the retained left testis was focally hyperechoic, with scant anechoic peritoneal and retroperitoneal free fluid. The dog was painful and reactive to ultrasound examination of the left caudal abdomen despite sedation. The right testis was located within the scrotum and was normal in size, shape, and echogenicity, measuring 0.85 × 1.44 cm. The prostate was enlarged, rounded, and hyperechoic, consistent with intact status. A small amount of non-shadowing echogenic material was in the urinary bladder lumen, consistent with cellular or crystalline urinary debris. The ultrasonographic diagnosis was unilateral, intra-abdominal left cryptorchid testicular torsion.

Figure 1.

A — Right lateral; B — Left lateral; and C — VD radiographs of the abdomen. A moderate amount of heterogeneous soft tissue and gas opaque mixed ingesta were within the stomach (S) and small intestines (SI), whereas the colon (C) was gas-filled. Gas-filled small intestinal loops (black arrowheads). The retained left testis was not visualized.

Figure 2.

A — Longitudinal ultrasonographic image of the normal descended right testis; B — Image of the retained left testis. C and D — Longitudinal ultrasonographic images of the retained left testis, epididymis, and spermatic cord, with and without power Doppler evaluation. The left testis was asymmetrically enlarged, rounded, and hyperechoic, with an enlarged, hypoechoic epididymis and spermatic cord (arrowheads), and hyperechoic surrounding mesentery. Absent flow signal within the left testis and epididymis on power Doppler.

Computed tomography (CT) was performed immediately following ultrasound to further confirm and add confidence to the diagnosis of testicular torsion before surgery, and to describe novel CT features of a non-neoplastic cryptorchid testicular torsion in a dog. Under sedation, pre- and post-contrast CT of the abdomen with intravenous nonionic iodinated contrast medium [2.2 mL/kg; Omnipaque (iohexol) 240 mg I/mL; GE Health Care, Princeton, New Jersey, USA] were performed in sternal recumbency using an 8-slice helical CT scanner (GE LightSpeed Ultra; GE Healthcare, Milwaukee, Wisconsin, USA). Soft tissue algorithm post-contrast delayed phase CT identified an ovoid, soft tissue attenuating, centrally non-contrast enhancing structure with a thin, mildly contrast enhancing peripheral rim caudal to the left kidney, correlating with the sonographically identified retained left testis (Figures 3, 4). The latter structure was enlarged (2.32 × 2.10 cm), and the spermatic cord was severely thickened, heterogeneous, minimally peripherally contrast enhancing, and tortuous. The proximal spermatic cord had a circuitous path with a partial “whirl” pattern (Figure 4) that abruptly tapered and was ill-defined caudally. Fat contiguous with the mesentery extended centrally along the testicular parenchyma and spermatic cord in a crescentic to triangular pattern (Figure 4). Scant non-contrast enhancing fluid attenuating material and fat stranding surrounded the retained left testis and spermatic cord. A mild amount of non-contrast enhancing free fluid was in the right cranial abdomen surrounding the duodenum and liver and within the retroperitoneal space adjacent to the right kidney. The normal right testis was identified within the scrotum, extending across midline to the left (Figure 3). The prostate was symmetrically enlarged and normal in attenuation with homogeneous contrast enhancement, consistent with intact status. Combined ultrasound and CT findings confirmed the diagnosis of unilateral intra-abdominal left cryptorchid testicular torsion.

Figure 3.

A and B — Pre- and post-contrast transverse CT images of the caudal abdomen at the level of L5, and C and D, at the level of the scrotum, acquired in a soft-tissue algorithm (soft-tissue window, WW-WL 281-22 HU). The retained left testis (white arrows) was caudal to the left kidney and was enlarged, ovoid, and soft tissue attenuating with a thin, mildly contrast enhancing peripheral rim. Scant peritoneal effusion and fat stranding were adjacent to the retained left testis (white arrowheads). The normal, descended right testis (black arrow) was within the scrotum, to the left of the penis. There is normal, homogeneous contrast enhancement of the descended right testis and epididymis.

Figure 4.

A — Post-contrast sagittal and B — Post-contrast dorsal, multiplanar reconstruction computed tomography images of the left caudal abdomen acquired in a soft-tissue algorithm (soft-tissue window, WW-WL 281-22 HU). The retained left testis (white arrows) was caudal to the left kidney (LK) and was enlarged, ovoid, and soft tissue attenuating with a thin, mildly contrast enhancing peripheral rim (top images). Bottom images demonstrate an ill-defined, partial whirl sign, characterized by tortuous, rotated testis and spermatic cord surrounded by a partial whirl of fat and soft tissue. Fat contiguous with the mesentery extended centrally along the testicular parenchyma and spermatic cord in a crescentic to triangular pattern (arrowheads). The spleen (SP) and urinary bladder (UB) are annotated. A small volume of iodinated positive contrast material was within the urinary bladder.

Exploratory laparotomy identified the intra-abdominal left testis cranial to the umbilicus and caudal to the left kidney. The testis and spermatic cord were grossly rotated along their long axis and discolored (dark blue/purple). An uncomplicated unilateral left cryptorchidectomy was performed via a midline laparotomy approach. Prophylactic IV cefazolin (22 mg/kg) was administered intraoperatively every 90 min, and carprofen (4.4 mg/kg) was administered subcutaneously once post-operatively. The left testis was not submitted for histopathology. Anesthetic recovery was uneventful, and the dog was discharged the following day with a 3-day course of oral carprofen (2.2 mg/kg) administered q12h. A 2-week post-operative recheck and suture removal were done at an alternative institution with no reported complications. Owner correspondence 1.5 y after surgery revealed that the dog had an uneventful recovery and underwent unilateral orchidectomy of his right descended testis at 2 y of age.

Discussion

This case report is the first to describe CT features of a non-neoplastic cryptorchid testicular torsion in a dog, with no other source identified after a search of multiple literature databases including PubMed, ResearchGate, and the Wiley Online Library. The incidence of cryptorchidism in dogs is variable and reported to be between 0.8 and 9.7% (1,2). Cryptorchidism is 2.7 times more likely to occur in small breed and purebred dogs; over-represented breeds include Chihuahuas, Yorkshire terriers, shih tzus, German shepherds, and boxers (1,3). The most common location of testicular cryptorchidism is the right inguinal region (37.9%), followed by the right abdomen (22.9%), left abdomen (10%), and bilateral intra-abdominal testes (6.3%) (1).

Abdominal cryptorchid testicular torsion in dogs most often occurs secondary to testicular neoplasia, specifically Sertoli cell tumors or seminomas, with a reported 36% incidence of torsion in neoplastic testes (4,5). It is thought that the increased weight of pendulous, neoplastic abdominal testes may predispose them to torsion (5). Torsion of a non-neoplastic cryptorchid testis is rare, and in reported cases, patients were young (< 1 y) with minimal biochemical abnormalities, apart from a leukocytosis (6–8).

Abdominal pain, lethargy, vomiting, hyporexia, and difficulty ambulating are among the most common clinical signs of testicular torsion in dogs (5). Diagnosis of testicular torsion can be challenging due to clinical signs mimicking other acute abdominal emergencies. Abdominal radiographs are insensitive for detection of cryptorchidism or testicular torsion, but a soft-tissue opaque mass caudal to either kidney or cranial to the urinary bladder may be inconsistently identified radiographically (6,7,9). Ultrasonography is a non-invasive, highly sensitive test to determine the location of retained testes, with 96.6% sensitivity for detecting abdominal testes and 100% positive predictive value for all testes located in abdominal or inguinal regions (2).

Sonographic characteristics of normal testes include coarse and homogeneous echotexture with a centrally located hyperechoic mediastinum testis, well-demarcated testicular capsule, and hyperechoic flecks of connective tissue (10). The epididymis is normally located dorsomedial to the testis, and the tail of the epididymis is most frequently hypoechoic (10). Non-neoplastic cryptorchid testes are often smaller, but have a similar shape, echogenicity, and echotexture compared to descended testes (4). In pathologic testes, the linear hyperechoic mediastinum testis is frequently maintained and used to identify the tissue origin (6).

Common sonographic findings of testicular torsion include testicular and epididymal enlargement with variable degrees of spermatic cord enlargement, ovoid to globoid testicular shape, testicular hypoechogenicity or rarely hyperechogenicity, and homogeneous to heterogeneous echotexture (8,11). Color Doppler ultrasonography is more specific and yields a higher diagnostic accuracy than B-mode ultrasonography for diagnosis of testicular torsion in men (8) and may demonstrate a decreased (incomplete torsion) or absence (complete torsion) of perfusion in the affected testis and spermatic cord (9,11). Within 6 h after the occurrence of acute testicular torsion, there may be epididymal enlargement and hypoechoic testicular parenchyma (8). After 1 to 10 d, testicular architecture becomes heterogeneous, and in testicular torsion present for > 10 d, the testis may be small and hypoechoic (8). In a study evaluating experimentally induced testicular torsion in dogs, the affected testes displayed gradual progressive enlargement and parenchymal heterogeneity, no perfusion on color or power Doppler, and no vascularity on contrast enhanced ultrasound (12). The most common sonographic features of testicular torsion were observed in this case, except for testicular hypoechogenicity. The cryptorchid testicular torsion in the case presented here had hyperechoic parenchyma, which has been reported rarely in dogs and men with acute testicular torsion (8).

Computed tomography is a more sensitive, specific, and accurate modality for localizing undescended testes in men compared to ultrasound (94, 100, and 96%, respectively for CT and 88, 100, and 91% for ultrasound), and may be helpful when sonographic findings are negative or equivocal (13). Contrast-enhanced CT is useful for evaluation of testicular perfusion in experimentally induced testicular torsion in rats and may be an alternative to ultrasound for diagnosing testicular torsion in indeterminate cases (14). Computed tomography features of neoplastic cryptorchid testicular torsion have been described in a dog, and include testicular enlargement, heterogeneous, reduced contrast enhancement, and a characteristic “whirl sign” demonstrated by the spermatic cord arranged in a whirl of fat and soft tissue striations (4). Computed tomography also has the ability to rule out pulmonary metastasis and may confirm and further localize other imaging findings such as metastatic lymphadenopathy (4).

In this case, CT was performed to add diagnostic confidence before surgery, further characterize the testicular torsion identified on ultrasound, evaluate testicular perfusion with IV contrast, and report novel CT features of a non-neoplastic cryptorchid testicular torsion in a dog. In this case, only a partial “whirl sign” was identified, likely due to the severely tortuous spermatic cord and volume averaging of overriding thickened tissue with regional peritoneal effusion and fat stranding. In addition to a partial whirl sign, fat extended centrally along the testicular parenchyma and spermatic cord in a crescentic to triangular pattern, similar to the previously reported sonographic finding of the hilar perivenous hyperechoic triangle in dogs with acute splenic torsion (15). This central testicular/spermatic cord crescentic to triangular fat pattern may be a useful feature in diagnosing dogs with non-neoplastic cryptorchid testicular torsion on CT. The remaining common CT features of testicular torsion were identified in this case and correlated well with sonographic findings. B-mode and color Doppler ultrasonography are the first choice for diagnosing testicular torsion due to the high sensitivity, accessibility, and lack of need for general anesthesia in canine patients. However, CT should be considered when ultrasonographic findings are inconclusive or indeterminate.

In conclusion, although non-neoplastic cryptorchid testicular torsion is rare in dogs, it should be considered in young intact male canine patients with non-specific clinical signs such as acute abdominal pain, lethargy, and emesis, particularly in the face of cryptorchidism. Contrast-enhanced CT features correlated well with sonographic findings, and allowed for rapid, accurate diagnosis and surgical planning of unilateral, non-neoplastic, intra-abdominal cryptorchid testicular torsion in a juvenile dog. CVJ