Portosystemic shunts are enlarged vessels that form collateral pathological
pathways between the splanchnic circulation and the systemic circulation.
Although their causes are multifactorial, portosystemic shunts all have one
mechanism in common-increased portal venous pressure, which diverts the blood
flow from the gastrointestinal tract to the systemic circulation. Congenital and
acquired collateral pathways have both been described in the literature. The aim
of this pictorial essay was to discuss the distinct anatomic and imaging
features of portosystemic shunts, as well as to provide a robust method of
differentiating between acquired portosystemic shunts and similar pathologies,
through the use of illustrations and schematic drawings. Imaging of
portosystemic shunts provides subclinical markers of increased portal venous
pressure. Therefore, radiologists play a crucial role in the identification of
portosystemic shunts. Early detection of portosystemic shunts can allow ample
time to perform endovascular shunt operations, which can relieve portal
hypertension and prevent acute or chronic complications in at-risk patient
populations.
ObjectiveTo assess the feasibility and reliability of apparent diffusion coefficient
(ADC) measurements of normal adrenal glands.Materials and methodsThis was a retrospective study involving 32 healthy subjects, divided into
two groups: prepubertal (PreP, n = 12), aged from 2 months
to 12.5 years (4 males; 8 females); and postpubertal (PostP,
n = 20), aged from 11.9 to 61 years (5 males; 15
females). Diffusion-weighted magnetic resonance imaging (DW-MRI) sequences
were acquired at a 1.5 T scanner using b values of 0, 20,
500, and 1000 s/mm2. Two radiologists evaluated the images. ADC
values were measured pixel-by-pixel on DW-MRI scans, and automatic
co-registration with the ADC map was obtained.ResultsMean ADC values for the right adrenal glands were 1.44 ×
10-3 mm2/s for the PreP group and 1.23 ×
10-3 mm2/s for the PostP group, whereas they were
1.58 × 10-3 mm2/s and 1.32 ×
10-3 mm2/s, respectively, for the left glands. ADC
values were higher in the PreP group than in the PostP group
(p < 0.05). Agreement between readers was almost
perfect (intraclass correlation coefficient, 0.84-0.94; p
< 0.05).ConclusionOur results demonstrate the feasibility and reliability of performing DW-MRI
measurements of normal adrenal glands. They could also support the
feasibility of ADC measurements of small structures.
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