Wandering

Torsion
of Wandering Spleen:

Importance
of Splenic Density and Liver to spleen attenuation ratio on CT

Introduction

Wandering spleen (WS) is a
rare entity that results from abnormal laxity or absence of the supporting
ligaments, with a reported incidence of <0.2% of patients undergoing splenectomy (1). It can occur in both sexes at any ages but has bimodal incidence distribution; mostly, children and childbearing women between the ages of 20 and 40 (2-4). Patients with WS may be asymptomatic or present with a mobile abdominal mass. Early clinical diagnosis of WS is difficult.  Delay in the diagnosis may lead to splenic torsion and infarction. Acute torsion which may lead to a fatal outcome is a surgical emergency, so imaging modalities play an important role in preoperative diagnosis. Evaluation of WS with torsion includes abdominal radiographs, ultrasound, and computed tomography (CT). Determination of splenic parenchyma viability is very important in deciding whether splenopexy rather than splenectomy is an option, especially in young children (5). Early diagnosis causes to perform more splenopexies and thus preserve more spleens. Contrast-enhanced (CE) CT in these cases provides information concerning the viability of the splenic parenchyma. We found a limited number of articles reporting the CT findings of torsion with subsequent infarction of WS (1,5-11). We didn't find any article reporting the CT attenuation values of spleen and the liver-to-spleen attenuation ratio (LSAR) of torsion with subsequent infarction of WS in English literature. Herein we report CE CT findings of WS with torsion in four patients and subsequent infarction in three of them. Patients and Methods; We reviewed the medical records and CT studies of four patients (three females, one male) diagnosed over a two-year period. CE CT was performed in all cases. CE abdominal CT was performed using 16 slice scanner in one patient (Somatom, Siemens) (Patient 1), 64 slice scanner (Aquilion, Toshiba Medical) in three patients (Patient 2, 3, 4), after intravenous nonionic contrast material (1 ml/kg) administration. CE CT images were obtained during portal venous phase and were reconstructed using a standard filtered back-projection algorithm with the following parameters: slice thickness, 2mm; slice interval 2mm; matrix size, 512x512 px. On multiplanar coronal reformatted CT images, we divided spleen into three equal parts as superior, middle, and inferior segments. We also divided each segment into two parts on axial images as anterior and posterior parts. Then six circular regions of interest (ROI) with a 1 cm diameter were placed within each parts of the spleen parenchyma, avoiding vessels and artifacts: two ROI in the superior anterior and posterior parts, two ROI in the middle anterior and posterior parts, and two ROI in inferior anterior and posterior parts, respectively (Table 1). Six ROI were placed within the hepatic parenchyma, with the same method: two ROI in the right lobe, two ROI in the left lobe, and two ROI in segment I and IV, respectively. The different attenuation values were averaged to obtain the mean attenuation of the liver and the spleen. LSAR was calculated (Table 2) (12). The size of the spleen was measured according to the calculation of the splenic index which is the product of its length, width, and thickness for all patients.  We also assessed the following findings for each patient; parenchymal enhancement, whirlpool sign, fat surrounding around splenic pedicle, capsular rim sign, intraperitoneal free fluid, spleen volume, enhancement of splenic artery and vein within pedicle. Measurement of the spleen volume was performed using Syngo.via software (Siemens, Forchheim, Germany). Patient 1: A 20 years old woman was admitted to the emergency department with acute abdominal pain. Physical examination revealed a mass in the left mid abdomen.  Routine blood tests were normal except for elevated white blood counts at 10.810 K/uL and C-reactive protein (CRP) at 1.12 mg/dl. Markedly enlarged and rotated nonenhancing spleen suggesting the diagnosis splenic infarction was observed on CE CT in the left mid abdomen, (Fig. 1). On surgery, the spleen appeared inferiorly displaced, congested and infarcted, and total splenectomy was performed. Histopathological examination confirmed the preoperative diagnosis. The post-operative recovery of the patient was uneventful, and she was discharged after six days.   Patient 2: A 22 years old male patient applied to emergency department with left lower quadrant pain for three days.  Physical examination showed tenderness and lump on left lower quadrant. Laboratory tests were within normal limits except for moderately elevated WBC (24300 K/uL). The CE CT of abdomen demonstrated the markedly enlarged nonenhancing spleen in the pelvis, which suggested the splenic infarction (Fig. 2,3). Laparotomy revealed a huge congested and infarcted spleen in the left pelvic region, measuring more than 25 cm in length, and splenectomy was performed. Histopathological examination demonstrated the congestion and hemorrhagic infarction. The post-operative recovery of the patient was uneventful, and he was discharged after three days later.    Patient 3: A 38 years old female admitted to the emergency department with abdominal pain. In physical examination, rebound tenderness and mobile mass in pelvic region were found. Routine blood tests were normal except for elevated white blood count 10.990K/uL and C-reactive protein (CRP) at 17,32 mg/dl The CE CT of abdomen demonstrated the markedly enlarged nonenhancing spleen in the pelvis which suggested the diagnosis of torsion with splenic infarction (Fig. 4). Laparotomy revealed a huge congested and infarcted spleen in the pelvic region, measuring more than 25 cm in length, and total splenectomy was performed. The splenic vessels were torsioned and a large thrombus was present in the splenic vein at the splenic hilum. There were multiple clock-wise turns of the splenic pedicle.  Histopathology demonstrated the congestion and hemorrhagic infarction. The post-operative recovery of the patient was uneventful and she was discharged four days later.    Patient 4: A 31 years old woman admitted to the hospital with fever and recurrent abdominal pain. Physical examination showed tenderness and mobile mass on the umbilical region. Routine blood tests were normal except for elevated white blood count 22410 K/uL and C-reactive protein 11.42mg/dl. Ultrasonography demonstrated enlarged displaced spleen in the left lower quadrant.  The CE CT of abdomen demonstrated the markedly enlarged enhancing spleen in the pelvis with whirlpool sign suggested the diagnosis of torsion without splenic infarction (Fig. 5). Splenopexy was recommended for this patient and she didn’t accept the surgery.  She was doing well with no abdominal symptoms at follow-up for six months. Results: The spleen was absent in the left upper quadrant of all cases, and a soft-tissue mass resembling the spleen in shape, size and density were present elsewhere in the abdomen. Soft tissue mass resembling spleen was seen in the left mid abdomen anterior to the left kidney in one case (Fig. 1) and in the pelvis adjacent to the bladder in three cases (Figs. 3, 4). We also detected parenchymal enhancement in one patient without infarction, the whirlpool sign in all patients, fat surrounding around splenic pedicle in three patients with infarction, capsular rim sign in one patient with infarction, intraperitoneal free fluid in all patients, enhancement of splenic artery in all patients and vein enhancement in one patients without infarction. The mean splenic volume was 889,5cm3 (range 651-1160 cm3). Table 3 provides a summary of CT findings of four cases.                Mean splenic density was measured as 40.77 HU (min 37.5 HU max 44.05 HU) in patients with infarction, 127.1 HU in a patient without infarction. LSAR was calculated as 2.55 (min 2.32, max 2.91) in patients with infarction, 0.99 in patient without infarction (Table 2). Three patients have undergone splenectomy surgery with preoperative diagnosis of infarction of WS which was confirmed by histopathological evaluation.  Discussion: WS is a congenital or acquired condition characterized by a hypermobile spleen. In both conditions, the pedicle involving splenic vessels appears to be longer than usual, resulting in torsion and consequent infarction.  Estrogen increase during pregnancy is thought to contribute to the laxity of the supporting structure, so WS is more common in multiparous women. Pediatric patients account for one-third of all cases (2). Clinical presentation varies from incidental pelvic mass to acute abdomen due to splenic infarct. Soleimani et al. reviewed literature from 1895 to 2005 and reported the most common complaint of 238 patients with wandering spleen was abdominal pain following by abdominal mass, vomiting, fever, and nausea, respectively (13). All of our cases presented with abdominal pain and fever. Laboratory tests are often nonspecific for diagnosing WS like those of our patients. Radiological imaging plays an important role in early diagnosis. The WS should be suspected in patients with the absence of spleen in the left hypochondrium and the presence of a soft-tissue mass resembling spleen in the lower abdomen. Sonography demonstrate the characteristic comma-shaped enlarged spleen in ectopic localization. Doppler ultrasonography is useful in the assessment of organ vascular supply. CT is the preferred study for diagnosing a WS when torsion is suspected clinically or on other imaging studies. Splenomegaly, poor or absent enhancement of splenic parenchyma, capsular rim and whirlpool sign are the CT findings of in wandering spleen with torsion. Splenomegaly which is nonspecific, but important sign of torsion was observed in all our patients. The whirlpool sign was defined as a specific finding for WS torsion, which also indicates an infarct may develop  (5). The whirlpool sign which was defined as a specific sign for splenic torsion in WS was observed in all our cases.  Capsular rim sign is another finding that the spleen capsule is more hyperdense than the parenchyma, has been identified for splenic infarction, probably due to collateral circulation (5). Capsular rim sign was observed in one case with splenic torsion and infarct. Intraperitoneal free fluid is another frequent finding that can be seen regardless of whether splenic ischemia develops or not. In all cases of our series, intraperitoneal free fluid, presumably reactive, was also detected. On CE CT, the absence of enhancement of spleen which indicates poor perfusion is an indirect sign of pedicle torsion and subsequent infarction. Unenhancement was observed in our 3 patients with infarction which was confirmed during surgery. We also detected parenchymal enhancement in one patient without infarction. We also calculated mean splenic density as 40.77 HU in 3 patients with infarction (min 37.53 HU, max 44. 05 HU), 127.1 HU in patient without infarction, The LSAR was calculated as 2.55 (min 2.32, max 2.91) in patients with infarction, 0.99 in patient without infarction (Table 2). It was reported that spleen’s attenuation was 55±4 HU; being equal or slightly lower (5–10 HU) lower than the liver density on an unenhanced scan. It shows homogenous enhancement during portal venous phase. The mean density of spleen was reported as max 166±28, min 116±28 on CE CT (14). Attenuation values of spleen in our patients with infarction (37.5; 40.8; 44.05 HU) were lower than the values reported on unenhanced and enhanced CT in English literature. Attenuation value of spleen in our patient without infarction was compatible with the values reported on CE CT in literature.  Shao et al reported diffuse decrease in spleen density in patients with acute pancreatitis which was an independent indicator of more severe condition (15). They reported that the reduction in spleen density in rats with severe acute pancreatitis was related to the increase in spleen volume. Abnormal hemoperfusion and microvascular disturbances that cause increased spleen volume were suggested as the cause of decreased spleen density.  The decreased spleen density in our patients with infarction may be explained by abnormal hemoperfusion and microvascular disturbances (15). LSAR is useful for the evaluation of hepatic steatosis index on noncontrast CT. Normal LSAR ratio was reported as 1.18± on nonenhanced CT.  Low LSAR represents increasing liver steatosis on noncontrast CT (16, 17). We didn’t find any article reporting LSAR values on contrast-enhanced CT. We calculated LSAR as 2.32, 2.42, 2.9 in patients with infarction, 0.99 in patients without infarction on CE CT during portal venous phase. Nonenhancement of spleen on CE CT may explain the higher LSAR values of our patients (2.32, 2.42, and 2.9) with infarction. Wandering spleen is a condition that needs to be treated surgically. Splenectomy is the treatment method in cases with ischemia or infarction, and splenopexy is the method that should be selected if the spleen is viable. Splenectomy was performed in 3 of our cases with torsion and infarction. Pathologically, ischemia and infarction were confirmed. Elective splenopexy has been recommended for the patient with spleen enhancement although torsion has developed, but the patient refused to be operated on and was followed up. Wandering spleen is a rare clinical condition which may cause fatal complications like torsion with subsequent infarction. Assessment of spleen viability is very important for determining the surgery protocol in which splenectomy is the usual treatment when a splenic infarction is detected, but splenopexy is chosen if the spleen is viable. CE CT is important for the assessment of the viability of spleen.   Why should an emergency physician be aware of this? Although WS is a rare clinical condition, it may cause fatal complication like torsion with subsequent infarction. WS should be considered in patients presented with abdominal pain and incidental mass in the lower abdominal quadrants. CECT should be obtained for the diagnosis of WS and assessment of the viability of spleen.  CECT could suggest the diagnosis of infarction of the spleen with following findings; absence of parenchymal enhancement, very low density of spleen (<45 HU), the liver to-spleen attenuation ratio which are greater than 2. Patients should be refered to general surgery if these findings are present. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.