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Knowledge of the histological features of different components of a liver lesion greatly assists radiologists because it provides understanding of the correspondingimaging features. The imaging characteristics of lesions depend on variations of the extracellular architecture, mainly surrounding stromal tissue. Until histological imaging techniques become available, cellular analysis relies on optical microscopy and immunohistochemistry. Recent advances in imaging techniques now provide additional information on lesions due to improved spatial, temporal and contrast resolution. Correct interpretation of these imaging features should improve diagnosis.

Fibrosis is one of the hallmarks of inflammatory and repair processes in pathology. Various exogenous and endogenous stimuli, including tumor development, can induce inflammatory reactions. During the post-equilibrium phase after IV injection of non specific contrast media, CT and/or MR allow the study of these inflammatory answers to tumoral or infectious processes. Delayed enhancement of collagenic fibrous tissue during the late post-equilibrium phase is an essential complementary data in the characterization of many liver lesions: cirrhosis, cholangiocarcinoma, focal nodular hyperplasia, fibrous metastasis. but also for the differential diagnosis of pancreatic diseases (groove pancreatitis vs ductal adenocarcinoma) or of gastro-intestinal diseases (gastric adenocarcinoma vs lymphoma, mechanical complication vs inflammatory bouts of ileal Crohn's disease).

A case of agenesis of the right lobe of the liver associated with portal hypertension is reported. This uncommon feature was diagnosed by computed tomography which excluded secondary liver atrophy due to cirrhosis or tumour. The main pathophysiological hypothesis for agenesis and portal hypertension, exceptionally associated, is arrest of hepatic development during foetal life.

The acquired or congenital nature of Riedel's lobe, a rare anomaly of hepatic lobulation, is a subject open to controversy. Normally asymptomatic, it presents as a palpable mass in the right hypochondrium leading to possible confusion with an hepatic or a renal tumor. Correct diagnosis can be established by the characteristic findings an ultrasonography. The typical anatomical and clinical features of this hepatic morphological variant are discussed in relation to ultrasound recordings obtained from three patients with a Riedel's lobe.