Encysted Odyssey: A Clinical and Pictorial Analysis of Hydatid Cysts From Head to Toe

Abstract

Introduction: Cystic echinococcosis, a zoonotic disease caused by the larval form of Echinococcus granulosus, predominantly affects the liver and lungs, with humans acting as accidental hosts.

Methods: Our retrospective study at the Department of Radiology and Imageology, Nizam's Institute of Medical Sciences, included 187 histopathologically or serologically proven cases. The mean age of presentation was 49.4 years.

Results: Liver involvement was most prevalent, accounting for 83.4% (n=156) of cases, followed by sporadic involvement of other organs such as the mesentery, spleen, pancreas, thalamus, kidney, lung, spine, and omentum. Characteristic diagnostic features observed on imaging included peripheral calcifications in 33% of cases, internal septations in 25% (n=47), dense calcifications in 15% (n=29), daughter cysts in 6% (n=11), and floating membranes in 5% (n=10). Among hepatic lesions, 90% (n=141) were showing involvement of a single lobe. Notably, 78% (n=110) of lesions were limited to the right lobe, 21% (n=30) to the left lobe, and 1% (n=1) to the caudate lobe. The most affected hepatic segment was segment VIII, while the least common was segment I (caudate lobe). Complications were identified in 13% (n=25) of cases of hepatic hydatidosis.

Conclusions: The findings of our study emphasize the systemic nature of E. granulosus infection which can affect various organs in the body. It also illustrates the invaluable insights imaging provides for timely and accurate diagnosis of hydatid disease.

Keywords: cross-sectional imaging; cystic echinococcosis; diagnostic imaging features; echinococcus granulosus; hydatid disease; radiology.

Figure 1. Varied organ distribution in hydatid disease

Figure 2. Mesenteric hydatid cyst

A 56-year-old male with mesenteric hydatid cyst presented with left upper quadrant pain increasing with exertion for four years. Topogram image (a), axial image (b), and coronal image (c) of non-contrast CT chest revealed a well-defined low attenuating fluid density consistent with thick-walled cystic lesion with dense peripheral calcifications noted in the left upper quadrant, which is seen arising from mesentery, causing indentation over stomach medially and spleen posteriorly.

Figure 3. Splenic hydatid cyst

A 40-year-old male with a splenic hydatid cyst presented with pain and swelling in the left hypochondrium. Axial plain (a), axial and coronal post-contrast (b and c) images showing a hypodense cystic lesion with ill-defined margins in splenic parenchyma showing thin intralesional septations with fine calcifications. The lesion is indenting on the fundus of the stomach and displacing the left kidney.

Figure 4. Biliary hydatid cyst

A 23-year-old female with a biliary hydatid cyst presented with fever, pain abdomen, jaundice, and deranged LFTs. Axial (a, b) and coronal (c, d, e) MRCP images showing T2 hypointensity in the dilated left hepatic duct, CHD, CBD with curvilinear soft tissue signal intensity contents within the CBD and IHBRD. LFTs: liver function tests; MRCP: magnetic resonance cholangiopancreatography; CHD: common hepatic duct; CBD: common bile duct; IHBRD: intrahepatic biliary radical dilatation

Figure 5. Pancreatic hydatid cyst

A 24-year-old female with pancreatic hydatid cyst presented with fever, cough, and shortness of breath for two months. Axial (a) and coronal (b) non-contrast CT abdomen revealed a well defined thin walled hypodense lesion of fluid attenuation with wall calcification measuring 6.5x6x6 cm noted along the distal body and tail of pancreas extending into lesser sac, laterally abutting the splenic hilum with few internal septations.

Figure 6. Intracranial thalamic hydatid cyst

A 70-year-old female with an intracranial thalamic hydatid cyst presented with headache, left-sided weakness, and vomiting for three months. Axial CT brain showing a well-defined hypodense lesion of +16HU with hyperdense rim involving the right thalamus causing a mass effect in the form of midline shift towards left and compression of bilateral lateral ventricles and the foramen of Monro resulting in hydrocephalus.

Figure 7. Renal hydatid cyst

A 45-year-old male with a renal hydatid cyst presented with pain in the right hypochondrium and right flank. Axial non-contrast (a, b), axial (c, d) and sagittal (e) post-contrast images show a large well defined predominantly exophytic heterogeneous hypodense lesion with focal peripheral wall calcifications with dense linear contents within noted arising from interpolar of right kidney, showing no post-contrast enhancement.

Figure 8. Spinal hydatid cyst

A 36-year-old male with a spinal hydatid cyst presenting with cough, fever, and back pain, Axial plain CT (a and b) and coronal (c), axial (d), and sagittal MRI (e and f) showing lytic lesions with well-defined cystic lesions with daughter cysts in spinous process, right transverse process and body of D3, D4 vertebral bodies. The lesion is scalloping the posterior end of the second rib on the right side (dotted arrow) causing bone expansion and projecting into the canal with narrowing and impingement of the cord.

Figure 9. Retroperitoneal hydatid cyst

A 26-year-old male with a retroperitoneal hydatid cyst presented with right flank pain and discomfort. Axial plain (a), axial post-contrast (b) and reformatted coronal post-contrast (c) CT showing a large well defined heterogeneously hypodense solid cystic multiloculated lesion in retroperitoneum with enhancing walls and internal septations with non-enhancing hypodense exophytic component, displacing bowel loops anteriorly, abutting and compressing IVC and aorta posteriorly with contact area >180 degrees. IVC: inferior vena cava

Figure 10. Pericardial hydatid cyst

A 32-year-old male with a pericardial hydatid cyst presented with fever, dry cough, chest pain, and severe exertional dyspnea for two weeks. Topogram image (a), axial image (b), and coronal image (c) of non-contrast CT chest revealed a well-defined hypodense (+30 to +36HU) lesion in the right para oesophagal region extending into the middle mediastinum and along the pericardium with loss of fat planes with underlying myocardium and adjacent major vessels.

Figure 11. Hydatid cyst involving rib

A 38-year-old male with a costal hydatid cyst presented with pain and swelling in the left chest wall for three years. Axial plain (a), axial post-contrast (b), and coronal post-contrast (c and d) images revealed a lobulated multilocular cystic lesion with few peripheral calcifications, located on the lateral aspect of the left seventh rib, associated with significant deformation and destruction of the internal compact layer of the rib with exophytic component seen extending into adjacent subcutaneous fat. Additionally, a calcified hepatic hydatid cyst is noted.

Figure 12. Ovarian hydatid cyst

A 40-year-old female with ovarian hydatid cyst presented with pelvic pain for three months. Axial (a) and coronal post-contrast (b and c) images revealed a large well-defined thin walled multi-loculated cystic lesion (+10HU) with multiple thin internal septations measuring 12.1x9.7x11.6 cm with thin hyperdense wall noted in pelvis more on left adnexa causing compression and displacement of bladder antero-superiorly with no enhancement on post contrast. The left ovary was not seen separately.

Figure 13. Frequency of distribution of diagnostic characteristics in various hydatid cysts in our demographic

Figure 14. Figure 14A showing lobar involvement in hepatic hydatid cysts and Figure 14B showing lobar distribution of hepatic hydatid cysts

Figure 15. Frequency of single segment involving hepatic hydatid cysts

Figure 16. Types of hepatic hydatid cysts with imaging features

CECT: contrast-enhanced computed tomography

Figure 17. Peritoneal hydatidosis

A 52-year-old male with peritoneal hydatidosis presented with progressively increasing abdominal distension, weight loss, and anorexia. Coronal (a,b) and axial (c) MRI abdomen showing multiple cystic lesions with peripherally arranged daughter cysts of varying sizes in the right lobe of the liver, subhepatic space, and visualized peritoneal cavity causing superior displacement of the diaphragm and causing compression of the right lower lobe. Cysts in the peritoneal cavity are compressing the pancreatic head and tail, bilateral kidneys with right minimal pleural effusion.

Figure 18. Complications of hydatid cysts

IHBRD: intrahepatic biliary radical dilatation

Figure 19. Comparison of organ distribution of cystic echinococcosis with previous studies

Figure 20. Biopsy specimen showing daughter cyst with inflammatory infiltrate