Clinical diagnosis
Case 163
【Progress】
She received gastric tube. She got intravenous drip infusion of lactate to improve dehydration. Abdominal echogram showed gradual dilatation of superior mesenteric vein. Paralytic ileus got improved.
【Discussion】
The total diameter of superior mesenteric vein (SMV) is usually larger than that of superior mesenteric artery (SMA). The SMA blood speed is rapid due to arterial pressure, while the SMV blood speed is slow and the SMV wall has thin thickness. Then, the blood volume is maintained by more dilatation of SMV diameter than SMA diameter. When the SMV blood volume is getting less, SMV diameter is getting more decreased than SMA diameter because the SMA diameter includes the thick SMA wall (1, 2).
The smaller SMV sign indicates the volume loss not only in SMV but also the volume loss in SMA. As lesions with the smaller SMV, there listed SMV thrombosis, SMA thrombosis, SMA embolism and non-occlusive mesenteric ischemia (NOMI) (3). Especially the smaller SMV sign is crucial to detect acute mesenteric ischemia (AMI) including SMV thrombosis, SMA embolism and SMA thrombosis. It is reported that sensitivity and specificity of smaller SMV sign for AMI are 70% and 95%, respectively (4). Meanwhile, the smaller SMV sign is also found in other causes rather than AMI such as dehydration, hypo-volume shock, end-stage cancer and ileus.
NOMI was reported as mesenteric ischemia with no evident occlusion of mesenteric arteries. NOMI occurs approximately 20 % of AMI (5). NOMI induces hypoperfusion of SMA irrigation and eventually bowel necrosis. It often requires extensive surgical resection of small bowel. The prognosis of NOMI was extremely poor: the mortality rate is over 50 % which is the worst of the AMI (5). The risk factors of NOMI are high age, dehydration, hypovolemic shock and renal dialysis (5, 6). It is believed that NOMI occur in spasm of SMA branches. The typical appearance of NOMI in angiography is sausage-like SMA branches (5, 6). The usefulness of enhanced MDCT using contrast medium is expected to be an alternative diagnostic tool instead of angiography (7, 8). MDCT also contributes to detect the presence or absence of ischemic changes of bowels such as bowel wall edematous thickness, mesenteric edema, bowel wall air and free air (7, 8). Early diagnosis and correct treatment such as intravenous injection of prostaglandin E1 are believed to elevate the survival rate of NOMI (8).
In our case, she was an eighty seven-year-old woman who was in a condition of dehydration. Dynamic enhanced MDCT using contrast medium showed markedly dilated small bowels like paralytic ileus and patent superior mesenteric artery. She received speedy treatment for dehydration inducing the dilatation of SMV diameter on MDCT the following day. Namely, when NOMI occurred, she was in-patient which enabled to make early diagnosis and to receive the prompt management. It was not necessary for her to be treated with prostaglandin E1 infusion and surgical resection. If not in-patient, the prognostic result might have been different.
【Summary】
We present an eighty seven-year-old woman in-patient for lumbago who experienced bloody diaper. Enhanced MDCT using contrast medium showed the smaller SMV sign, ileus-like dilated small bowel and patent SMA, indicative of diagnosis of suspicious NOMI. The drip infusion for dehydration was conducted, inducing the dilatation of SMV the following day. The smaller SMV sign is crucial to detect acute mesentery ischemia (AMI), especially superior mesenteric occlusion (sensitivity 70%, specificity 95%). NOMI occurs in approximately 20% of AMI and can cause extensive necrosis of the bowel, and the prognosis is very poor , over 50% mortality rate, worst of the AMI. The risk factors of NOMI are high age, dehydration, hypovolemic shock and renal dialysis. In our case, when suspicious NOMI occurred, she was in-patient which enabled to make early diagnosis and to receive the prompt management. When the diagnosis was late, the prognostic result might have been different.
【References】
1.Clair DG, et al. Mesenteric ischemia. N. Engl. J. Med. 2016; 374: 959–68.
2.Kanasaki S, et al. Acute Mesenteric Ischemia: Multidetector CT Findings and Endovascular Management. Radiographics. 2018 May-Jun;38(3):945-961.
3.Furukawa A, et al. CT diagnosis of acute mesenteric ischemia from various causes. AJR Am J Roentgenol. 2009;192 (2): 408-16.
4.Takaaki Nakano, et al. Accuracy of the smaller superior mesenteric vein sign for the detection of acute superior mesenteric artery occlusion. Acute Med Surg. 2018 Apr; 5(2): 129–132.
5.Mazzei MA, et al. Reperfusion in non-occlusive mesenteric ischaemia (NOMI): effectiveness of CT in an emergency setting. Br J Radiol. May 2016; 89(1061): 20150956.
6.Trompeter M, et al. Non-occlusive mesenteric ischemia: etiology, diagnosis, and interventional therapy. Eur Radiol 2002; 12: 1179–87.
7.Woodhams R, et al. Usefulness of multidetector-row CT (MDCT) for the diagnosis of non-occlusive mesenteric ischemia (NOMI): assessment of morphology and diameter of the superior mesentericartery (SMA) on multi-planar reconstructed (MPR) images. Eur J Radiol 2010;76:96–102.
8.Mitsuyoshi A, et al. Survival in Nonocclusive Mesenteric Ischemia. Early Diagnosis by Multidetector Row Computed Tomography and Early Treatment With Continuous Intravenous High-dose Prostaglandin E1. Ann Surg. 2007 Aug; 246(2): 229–235.
2019.9.25