A 42-year-old woman was admitted through our emergency department for subacute onset of lower abdominal pain in September 2014. Bedside ultrasound by a gynaecology specialist showed a left adnexal cyst with fluid interface. Magnetic resonance imaging of the pelvis showed a large well-defined multiloculated cystic lesion measuring 9.2 cm (width) × 8.5 cm (depth) × 8.9 cm (height) with thick T1 and T2 hypointense enhancing wall and septa at the left side of the pelvis (Fig 1). An internal slightly T1 hyperintense component with fluid-fluid level was suspected to be proteinaceous or haemorrhagic content. A 1.6-cm non-enhancing mural nodule was noted at the posterior aspect. Partial bicornuate uterus was noted. Bilateral ovaries were normal in size with small cysts (Fig 2). Laparoscopy was done, with excision of the lesion. Intra-operative frozen section showed a benign spindle cell tumour. Final histopathological evaluation revealed a retroperitoneal schwannoma.

The majority of cystic pelvic masses originate from the ovary. Mimics of ovarian cystic masses have a wide variety of diagnoses. It is important to understand the relationship of a mass with its anatomic location, identify normal ovaries at imaging, and correlate imaging findings with the patient’s clinical history to avoid misdiagnosis.

Retroperitoneal schwannoma is a rare tumour and is difficult to diagnose, accounting for only 6% of retroperitoneal neoplasms. A retroperitoneal schwannoma is usually located in the paravertebral space or pre-sacral pelvic retroperitoneum.1 It usually occurs in young to middle-aged adults, and women are affected twice as often as men.1 The patient is usually asymptomatic, or complains of a wide variety of non-specific symptoms when the tumour is large in size.2 Malignant transformation is rare.1 On magnetic resonance images, a schwannoma appears as a well-defined mass with hypo- or iso-intensity on T1-weighted images and with hyperintensity on T2-weighted images. The nerve of origin is often difficult to identify. It is not unusual for a schwannoma to display cystic changes. However, prominent cystic changes are uncommon and point to ancient schwannoma, a rare variant of schwannoma that is characterised by degeneration and decreased cellularity.3 On magnetic resonance images, ancient schwannoma appears as a well-defined, complex cystic mass with a variable enhancement pattern. Thick T1 and T2 hypointense enhancing wall and septa correspond to a fibrous capsule, consisting of epineurium and residual nerve fibres.4

Identification of the nerve adjacent to or along the tumour is useful for differentiating ancient schwannomas from other complex cystic lesions, such as serous or mucinous cystadenocarcinoma, abscess, necrotic soft-tissue sarcoma, or necrotic metastatic lymphadenopathy.5

In the present case, the patient did not complain of any neurological symptoms at presentation. The presence of normal ovaries and fibrous capsule indicated a preoperative diagnosis of ancient schwannoma. This case illustrates the importance of considering this uncommon diagnosis when a pelvic complex cystic lesion is detected in imaging, and seeking specific imaging features (such as fibrous capsule and close relationship to the nerve) to confirm or exclude this diagnosis. This would facilitate surgical planning and minimise the risk of complications such as major neurological deficit.

All authors contributed to the concept or design, acquisition of data, analysis or interpretation of data, drafting of the manuscript, and critical revision for important intellectual content. All authors had full access to the data, contributed to the study, approved the final version for publication, and take responsibility for its accuracy and integrity.

All authors have disclosed no conflicts of interest.

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

1. Rha SE, Byun JY, Jung SE, Chun HJ, Lee HG, Lee JM. Neurogenic tumors in the abdomen: tumor types and imaging characteristics. Radiographics 2003;23:29-43. Crossref

2. Kim SH, Choi BI, Han MC, Kim YI. Retroperitoneal neurilemoma: CT and MR findings. AJR Am J Roentgenol 1992;159:1023-6. Crossref

3. Dahl I. Ancient neurilemmoma (schwannoma). Acta Pathol Microbiol Scand A 1977;85:812-8. Crossref

4. Takeuchi M, Matsuzaki K, Nishitani H, Uehara H. Ancient schwannoma of the female pelvis. Abdom Imaging 2008;33:247-52. Crossref

5. Isobe K, Shimizu T, Akahane T, Kato H. Imaging of ancient schwannoma. AJR Am J Roentgenol 2004;183:331-6. Crossref

A 54-year-old man who was an ex-smoker was admitted to Pok Oi Hospital in August 2015 with acute chest pain that was subsequently confirmed to be a non-ST elevation myocardial infarction. Echocardiogram revealed anterior wall hypokinesia. Computed tomography (CT) coronary angiography demonstrated chronic total occlusion of the right coronary artery and a 90% stenotic lesion in the proximal to mid left anterior descending artery that was deemed to be the culprit lesion. Percutaneous coronary intervention was subsequently performed with a drug-eluting stent deployed across the proximal to mid left anterior descending artery stenosis. Angiographic results were excellent.

At clinical follow-up, the patient complained of persistent chest discomfort. Repeated echocardiogram was unremarkable showing normal left ventricular function without any regional wall motion abnormality. A CT stress myocardial perfusion and viability study was requested to guide subsequent management. The study protocol included quantitative evaluation of myocardial perfusion with pharmacological stress using a dynamic approach, followed by a delayed scan for the presence or absence of late myocardial enhancement.

Adenosine stress myocardial perfusion study with colour-coded maps demonstrated perfusion defects in the apicoseptal segment, the mid-inferoseptal segment, and to a lesser extent the basal inferoseptal segment (Fig 1). For quantitative evaluation, the normal areas had a myocardial blood flow of approximately 128 mL/100 mL/min, whereas areas with ischaemia had a flow of around 40 mL/100 mL/min. No delayed enhancement of the corresponding segments was evident to suggest scarring due to prior myocardial infarction (Fig 2).

Eventually the patient underwent a percutaneous coronary intervention to the chronic total occlusion of the right coronary artery in 2016 via a combined radial and femoral arterial approach with successful stent deployment across the occluded segment. Final angiography showed excellent results with mild residual stenosis in patent ductus arteriosus ostium (Fig 3). To date, the patient remains symptom-free with improvements in both his exercise tolerance and mood, and psychiatric reports revealing reduced dosage of antidepressants.

Various imaging modalities are available for stress myocardial perfusion assessment.1 The present case demonstrates how a state-of-the-art dynamic and quantitative assessment of myocardial perfusion using a dual-source CT scanner enables detection of ischaemia along with viability assessment in a rapid and non-invasive fashion within an acceptable radiation dose.2

Conventional “static” CT myocardial imaging allows visual qualitative assessment of a single snapshot of myocardial iodine contrast attenuation that requires precise timing of the arrival of contrast to preserve diagnostic integrity. With a dual-source CT, quantitative assessment of myocardial perfusion in multiple cardiac phases with precise anatomic localisation of the ischaemic area becomes possible. To date, many studies have assessed the reliability of dual-source multiple-detector CT in the dynamic and quantitative evaluation of myocardial perfusion.2 3 4 5

Stress CT myocardial perfusion is emerging as a potentially promising non-invasive technique to detect myocardial ischaemia both qualitatively and quantitatively. With new-generation multiple-detector CT scanners, a one-stop non-invasive comprehensive evaluation of the heart including the coronary artery, ventricular function, myocardial perfusion, and viability is possible. Stress CT myocardial perfusion provides incremental benefit to standard coronary CT angiography, particularly for intermediate coronary lesions.2

All authors had full access to the data, contributed to the study, approved the final version for publication, and take responsibility for its accuracy and integrity.

Concept or design: All authors.
Acquisition of data: A Li, YH Chan.
Analysis of data: A Li, YH Chan.
Drafting of manuscript: A Li, YH Chan.
Critical revision for important intellectual content: All authors.

All authors have disclosed no conflicts of interest.

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

1. Ko SM, Hwang HK, Kim SM, Cho IH. Multi-modality imaging for the assessment of myocardial perfusion with emphasis on stress perfusion CT and MR imaging. Int J Cardiovasc Imaging 2015;31(Suppl 1):1-21. Crossref

2. Rossi A, Dharampal A, Wragg A, et al. Diagnostic performance of hyperaemic myocardial blood flow index obtained by dynamic computed tomography: does it predict functionally significant coronary lesions? Eur Heart J Cardiovasc Imaging 2014;15:85-94. Crossref

3. Kim SM, Choi JH, Chang SA, Choe YH. Additional value of adenosine-stress dynamic CT myocardial perfusion imaging in the reclassification of severity of coronary artery stenosis at coronary CT angiography. Clin Radiol 2013;68:659-68. Crossref

4. Bamberg F, Becker A, Schwarz F, et al. Detection of hemodynamically significant coronary artery stenosis: incremental diagnostic value of dynamic CT-based myocardial perfusion imaging. Radiology 2011;260:689-98. Crossref

5. Varga-Szemes A, Meinel FG, De Cecco CN, Fuller SR, Bayer RR 2nd, Schoepf UJ. CT myocardial perfusion imaging. AJR Am J Roentgenol 2015;204:487-97. Crossref

The incidence of inflammatory bowel disease, particularly Crohn’s disease, is rising in Hong Kong.1 The age-adjusted incidence of Crohn’s disease increased from 0.01 per 100 000 population in 1985 to 1.46 per 100 000 population in 2014.1 Crohn’s disease is a multisystem disorder with specific radiological features such as transmural inflammation, fistulation, and skip lesions. Perianal fistulas often complicate Crohn’s disease, affecting up to 36% of patients.2

Infliximab, a monoclonal antibody against tumour necrosis factor-α, has revolutionised the treatment of Crohn’s disease–related anal fistula. Current evidence shows encouraging results for closure of perianal fistulas. According to a local consensus statement, biologics are advocated in patients with active fistulising Crohn’s disease, particularly those with complex perianal fistulising disease.3

Response to monoclonal antibody therapy needs to be monitored. This pictorial review illustrates the post-treatment changes on magnetic resonance imaging (MRI) of anal fistula in patients prescribed infliximab.

Patients with a known history of Crohn’s disease complicated by perianal fistula and prescribed infliximab between 2012 and 2016 were reviewed. The treatment regimen at our centre comprises an intravenous loading dose of infliximab 5 mg/kg, followed by the same dose at week 2 and week 6. Thereafter a maintenance dose of 5 mg/kg is given every 8 weeks.

Magnetic resonance images were acquired with the 1.5T Siemens Magnetom Avanto system (Erlangen, Germany). The pelvic MRI protocol for perianal fistula evaluation consists of T1-weighted and high-spatial-resolution T2-weighted imaging sequences without fat saturation to delineate the muscle groups, fat planes, and fistula tract. T2-weighted imaging with fat suppression is used to assess oedema and fluid-containing tracts and cavities, whereas fat-suppressed T1-weighted unenhanced and contrast-enhanced sequences are used to assess the presence and degree of inflammation (Table). Diffusion-weighted imaging is not routinely performed in view of the need for an extended examination time. Information about the presence of fluid, oedema, cavities, and inflammation can be obtained through these sequences. Anal fistulae are classified according to the Parks’ classification system (Fig 1).4

Three patients (two men, one woman) were reviewed and all received infliximab. At least one pre-treatment and one post-treatment MRI were performed.

Patient A was a 34-year-old woman with a history of systemic lupus erythematosus, retinitis, and neuropsychiatric lupus. She had had recurrent ischiorectal abscess and perianal fistula since 2002. Rectal biopsy confirmed Crohn’s disease. Despite treatment with azathioprine, the perianal fistula failed to close. She was scheduled to initially receive three doses of infliximab. Close monitoring was essential in view of the potential to develop lupus-like disease. Progress MRI after the third dose of infliximab showed slight interval improvement in her perianal fistula. Biologics were continued in view of the residual disease. After the seventh dose of infliximab, progress MRI revealed a largely quiescent perianal fistula (Fig 2). In view of the radiologically healed fistula, clinical improvement and potential risk of lupus-like disease, the decision was taken to stop the infliximab infusion but continue close clinical and radiological monitoring.

Patient B was a 24-year-old man with a history of perianal fistula since 2015 and an episode of perianal abscess that required incision and drainage. Crohn’s disease was confirmed on rectal biopsy. He had previously developed azathioprine-induced pancytopenia. Subsequent infusion of infliximab infusion resulted in responsive disease, evident on MRI (Fig 3). Clinical and radiological monitoring (progress MRI) at 6-month intervals was carried out to determine progress of the perianal fistula. Infliximab would be stopped when there was evidence of healed tract and clinical improvement.

Patient C, a 42-year-old man had a history of ileocolic Crohn’s disease since 2008, with episodes of perianal abscess and fistula refractory to steroid and azathioprine treatment. Magnetic resonance imaging showed progressive perianal fistula (Fig 4) after the second maintenance dose of infliximab. Previous infliximab dose/frequency was continued and progress MRI planned for the purpose of reassessment and consideration of alternative treatment if there was persistent progression.

Crohn’s disease–related anal fistulae are frequently encountered in radiologic practice due to their complexity and propensity for incomplete treatment response and relapse.

Magnetic resonance imaging is a well-established diagnostic tool for anal fistula. Its inherent high spatial and contrast resolution allows precise anatomical delineation.5 Magnetic resonance imaging plays a critical role in helping determine the appropriate treatment that should be individualised according to the type of perianal fistula and the degree of involvement of surrounding pelvic structures. Clinical examination can often be difficult because of induration and inflammation in patients with anal sepsis. At MRI, identification and localisation of the entire fistula, including the external opening, the primary track, secondary tracks, abscesses, and the internal opening, are essential for fistula classification and treatment. Inadequate assessment may result in progression of a simple fistula to a complex fistula, and failure to recognise secondary extensions can result in recurrent sepsis. Anti–tumour necrosis factor antibodies (infliximab) have been introduced with good clinical results. Magnetic resonance imaging also plays an important role in evaluation of the response to medical therapy. Magnetic resonance imaging does not have field of view limitations and offers excellent views of the supralevator, retrorectal and anteroanal spaces, where occult sepsis may be missed clinically due to extensive scarring or a remote location.6

This pictorial review demonstrates the ability of MRI to monitor the response to therapy of anal fistula in Crohn’s disease patients receiving infliximab.

KY Man is responsible for the design, acquisition and interpretation of data, and drafting of the article. EMF Wong, FKY Cho, and CM Leung are responsible for critical revision for important intellectual content.

All authors have disclosed no conflicts of interest. All authors had full access to the data, contributed to the study, approved the final version for publication, and take responsibility for its accuracy and integrity.

1. Ng SC, Leung WK, Shi HY, et al. Epidemiology of inflammatory bowel disease from 1981 to 2014: results from a territory-wide population-based registry in Hong Kong. Inflamm Bowel Dis 2016;22:1954-60. Crossref

2. Leong RW, Lau JY, Sung JJ. The epidemiology and phenotype of Crohn’s disease in the Chinese population. Inflamm Bowel Dis 2004;10:646-51. Crossref

3. Leung WK, Ng SC, Chow DK, et al. Use of biologics for inflammatory bowel disease in Hong Kong: consensus statement. Hong Kong Med J 2013;19:61-8.

4. Parks AG, Gordon PH, Hardcastle JD. A classification of fistula-in-ano. Br J Surg 1976;63:1-12. Crossref

5. Buchanan G, Halligan S, Williams A, et al. Effect of MRI on clinical outcome of recurrent fistula-in-ano. Lancet 2002;360:1661-2. Crossref

6. Bell SJ, Halligan S, Windsor AC, Williams AB, Wiesel P, Kamm MA. Response of fistulating Crohn’s disease to infliximab treatment assessed by magnetic resonance imaging. Aliment Pharmacol Ther 2003;17:387-93. Crossref

An 80-year-old man presented to the emergency department in August 2016 with a 2-day history of painful scrotal swelling and fever. There was no history of trauma. He had a history of hypertension, diabetes mellitus and bullous pemphigoid, and was taking long-term steroid therapy. Upon presentation, the patient had a fever of 38.8°C and fast atrial fibrillation with a heart rate of 170 beats per minute. Blood pressure was 149/104 mm Hg. Physical examination of the patient revealed scrotal skin erythema and a firm left scrotal swelling that was tender on palpation. No cough impulse could be elicited. His white cell count was 21.8 × 109 /L and blood glucose level was 21.6 mmol/L. Ultrasound of the left hemiscrotum showed a fluid collection with hyperechoic interfaces and ring-down artefact suggestive of the presence of gas, obscuring the underlying structures (Fig 1). Subsequent non-contrast computed tomographic scan of the pelvis confirmed that the mottled gas and fluid density were confined to the left hemiscrotum (Fig 2a). The left testis and epididymis were poorly delineated. There was no gas density in the subcutaneous layer of the scrotum or perineum or in the intraperitoneal cavity. There was also no evidence of indirect inguinal hernia (Fig 2b). A diagnosis of emphysematous epididymo-orchitis was made. Emergency surgery was arranged a few hours after imaging. Intra-operatively, gas and pus were seen within the left tunica vaginalis. The left epididymis was necrotic and almost destroyed but the left testis was relatively spared with friable tissue and patches of necrosis (Fig 3). Drainage of pus and left orchidectomy were performed. Pus culture revealed Escherichia coli. The patient subsequently developed septic shock and died 3 days after the operation.

Emphysematous cholecystitis, pyelonephritis, and cystitis are not uncommonly seen in patients with poorly controlled diabetes mellitus. It is nonetheless rare to see gas-forming infection of the epididymis and testis although this is also reported to be associated with diabetes mellitus.1 2 3 Long-term use of steroid in our patient may have been an additional risk factor due to immunosuppression. Based on the clinical presentation and ultrasound findings of our patient, the main differential diagnoses included Fournier’s gangrene and incarcerated indirect inguinal hernia. Computed tomographic scan was very helpful in delineating the definitive diagnosis. Gas pockets confined to the scrotal sac without involvement of the subcutaneous layer of the perineum virtually excluded the possibility of Fournier’s gangrene. Incarcerated indirect inguinal hernia was excluded due to the absence of bowel loops in the scrotal sac.

When a diabetic patient presents with acute scrotal pain and features of infection, careful examination during the initial ultrasound scan for the presence of gas within the scrotum is essential as this will alter the subsequent management plan as it implies a much poorer prognosis than non–gas-forming epididymo-orchitis.

In conclusion, emphysematous epididymo-orchitis is an uncommon but life-threatening disease. Ultrasound and computed tomographic scan are essential to identify this entity for early treatment.

All authors have made substantial contributions to the concept or design of this study; acquisition of data; analysis or interpretation of data; drafting of the article; and critical revision for important intellectual content.

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

All authors have disclosed no conflicts of interest. All authors had full access to the data, contributed to the study, approved the final version for publication, and take responsibility for its accuracy and integrity.

1. Mathur A, Manish A, Maletha M, Luthra NB. Emphysematous epididymo-orchitis: a rare entity. Indian J Urol 2011;27:399-400. Crossref

2. Mandava A, Rao RP, Kumar DA, Naga Prasad IS. Imaging in emphysematous epididymo-orchitis: a rare cause of acute scrotum. Indian J Radiol Imaging 2014;24:306-9. Crossref

3. Hegde RG, Balani A, Merchant SA, Joshi AR. Synchronous infection of the aorta and the testis: emphysematous epididymo-orchitis, abdominal aortic mycotic aneurysm, and testicular artery pseudoaneurysm diagnosed by use of MDCT. Jpn J Radiol 2014;32:425-30. Crossref

A 43-year-old Chinese man presented to United Christian Hospital, Hong Kong, in January 2016, with a 2-year history of vague right upper quadrant pain. Blood test results were unremarkable except for an episode of transient eosinophilia. Ultrasonography showed mildly dilated intrahepatic ducts. Magnetic resonance cholangiopancreatography showed diffuse and uniform mild dilatation of peripheral intrahepatic bile ducts (Fig 1) consistent with the ‘too many intrahepatic ducts’ sign (Fig 2). Notably, there was no central extrahepatic bile duct dilatation. Subsequently requested stool microscopy was positive for Clonorchis sinensis ova. The patient was given a course of praziquantel.

Clonorchiasis is a foodborne zoonosis caused by consumption of raw or undercooked freshwater fish infested by the liver fluke C sinensis. C sinensis larvae penetrate the scales of freshwater fish and encyst in subcutaneous tissues. Cysts, when consumed by a definitive host, hatch in the intestine and migrate to the biliary tree, where the adult flukes establish residence. Clonorchiasis is endemic in many parts of Asia, including China, Korea, and Vietnam.1 Clonorchiasis and its complications are not commonly seen in affluent populations, such as those in Hong Kong. However, the increasing mobility of people around the region means that clinicians should be vigilant of the condition and alert to its symptoms. Knowledge of the characteristic imaging features of clonorchiasis would prompt stool microscopy and allow early diagnosis.

Within the biliary tree, adult C sinensis flukes reside in small- or medium-sized peripheral intrahepatic ducts. The organisms cause dilatation of the intrahepatic ducts. In heavy infestations, the extrahepatic ducts, the gallbladder, or even the pancreatic duct can also be involved. The dilated peripheral ducts can be visualised by direct cholangiography, or to a better extent by magnetic resonance cholangiopancreatography (owing to the independence of rate and volume of the contrast injection), as the ‘too many intrahepatic ducts’ sign.2 Occasionally, linear or elliptical filling defects representing the flukes can be seen.3

Light infestations with C sinensis can be asymptomatic. Heavier infestations can result in fever, jaundice, right upper quadrant pain, and eosinophilia. Untreated, chronic clonorchiasis induces chronic inflammation of the bile ducts. Recurrent pyogenic cholangitis, cholelithiasis, pancreatitis, and cholangiocarcinoma are the main complications.4

Infestations are diagnosed by observation of C sinensis ova during stool microscopy. Immunological and molecular techniques of diagnosis are still at the experimental stage.1 Praziquantel is the only drug treatment for clonorchiasis that is recommended by the World Health Organization.1

In summary, clinicians in Asia should be vigilant of clonorchiasis. In modern clinical practice, magnetic resonance cholangiopancreatography is often requested for non-invasive evaluation of the biliary tree. Knowledge and recognition of the characteristic imaging features of clonorchiasis would prompt timely investigation by stool microscopy. Early diagnosis and treatment of clonorchiasis can prevent complications such as recurrent pyogenic cholangitis and cholangiocarcinoma.

The authors have no conflicts of interest to disclose.

1. World Health Organization. Foodborne trematode infections—clonorchiasis. Available from: http://www.who.int/foodborne_trematode_infections/clonorchiasis/en/. Accessed on 27 Nov 2016.

2. Choi D, Hong ST. Imaging diagnosis of clonorchiasis. Korean J Parasitol 2007;45:77. Crossref

3. Lim JH. Radiologic findings of clonorchiasis. AJR Am J Roentgenol 1990;155:1001-8. Crossref

4. Choi BI, Han JK, Hong ST, Lee KH. Clonorchiasis and cholangiocarcinoma: etiologic relationship and imaging diagnosis. Clin Microbiol Rev 2004;17:540-52. Crossref