Teaching Case

The patient presented with a small adenocarcinoma of the rectum. A triphasic spiral CT scan was performed for further preoperative tumour staging. Laboratory studies, including liver function tests, were unremarkable.

The patient consulted his physician complaining of abdominal cramps and bloody stools. He had no pertinent medical history and was not taking any medication. Laboratory studies, including liver function tests, were unremarkable. Colonoscopy showed a small tumour of the rectum. Pathological examination of biopsies proved this tumour to be an adenocarcinoma. A CT scan of the abdomen was requested for further preoperative staging.

Triphasic spiral CT scan of the abdomen was performed. On images before the administration of IV contrast a large ovoid lesion, measuring up to 5.3cm, was visible in the liver (Fig. 1). The lesion had a hypodense centre with a slightly hyperdense rim, in comparison with the normal surrounding liver parenchyma. No clear enhancement was noted in the arterial phase after the administration of IV contrast (Fig. 2) . In the venous phase there was irregular enhancement of the margins, while the centre of the lesion showed no uptake of contrast medium at all (Fig. 3). There was no evidence for hepatic or portal vein thrombosis. The adenocarcinoma of the rectum was visible as a hyperattenuating focal thickening of the ventral rectal wall (Fig. 4). There were no enlarged lymph nodes.

Differential diagnosis for the hepatic lesion included abscess, haemorrhagic adenoma, lymphoma and metastasis. Because a metastasis of the rectal carcinoma needed to be ruled out, a CT-guided liver biopsy (14G needle) was performed (Fig. 5). There were no complications after the procedure. Pathological examination showed blood-filled spaces with no endothelial lining, characteristic of peliosis hepatis.

Peliosis hepatis is an uncommon benign disorder of the liver, characterised by oval and irregularly shaped blood-filled spaces, which are lined either by hepatocytes or endothelial cells. The cavities range in size from less than 1mm to several centimetres and have no preferential location within the hepatic lobule. These cavities communicate with the sinusoids, many of which are dilated. Peliosis most often involves the liver, but the entity may affect other organs of the reticuloendothelial system such as the spleen, the lymph nodes or the bone marrow.

The pathogenesis of peliosis hepatis is unclear. A number of theories have been postulated to explain the aetiology, such as outflow obstruction of the blood flow at the sinusoidal level, hepatocellular necrosis, or direct lesions of the sinusoidal barrier.

Peliosis hepatis commonly occurs in patients treated with anabolic steroids, corticosteroids or oral contraceptives. The disease is also frequently associated with a variety of other conditions such as chronic waste states, chronic disease, cancer, tuberculosis, renal and cardiac transplantation, diabetes, Hodgkin's disease, AIDS and exposure to toxic agents.

Several authors have reported resolution of peliosis hepatis after treatment of the associated disease. In about 25-50% of cases no known associated risk factor can be found.

Peliosis hepatis seldom causes clinical symptoms and is frequently discovered incidentally, as in this patient. However, the disorder can uncommonly result in hepatic failure, cholestasis, portal hypertension, haemorrhage and even spontaneous hepatic or splenic rupture.

The appearance on CT scans can be confusing because of its variable presentation from multiple small lesions with variable enhancement to larger and even solitary lesions as described in this case. On precontrast CT images the lesions are usually iso- to hypodense compared with the surrounding liver parenchyma. In some cases hyperdense spots are found in these lesion, representing focal haemorrhage. Following contrast injection the lesions are hypoattenuating. During a later venous stage the liver mostly becomes homogeneous again.

According to Maves et al. the multiple hepatic foci in peliosis hepatis show a high signal on T2-weighted images and a variable signal on T1- and proton density- weighted images, presumably reflecting various stages of subacute haemorrhage. However, the findings of Jamadar et al. do not confirm this as they described a case where the MRI scan (T1-, T2- and STIR-weighted images) showed no abnormality of the liver at all.

According to some authors, angiography can be of use since it can differentiate peliosis hepatis from a vascular malformation or tumour. Angiography shows multiple round collections of contrast material, best seen in the late arterial phase.

Histology is the only certain way of making the diagnosis, as all imaging modalities available are not sufficiently specific. The risk of performing a needle biopsy in peliosis hepatis is unclear. Severe haemorrhage and even fatal outcome following needle biopsy have been reported. Therefore biopsy should be avoided when possible.

Although peliosis hepatis is considered a rare disorder, we believe radiologists can expect to see more cases because of the increasing prevalence of its associated conditions. By knowing its appearance on different imaging modalities the radiologist can lead the way in diagnosing this condition.