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ORIGINAL ARTICLE
Year : 2013  |  Volume : 16  |  Issue : 4  |  Page : 154-159

Helical computerized tomography of the abdomen: Indications and spectrum of findings in a tertiary health center


Department of Radiology, Usmanu Danfodiyo University Teaching Hospital, Sokoto, Nigeria

Date of Web Publication21-Jan-2014

Correspondence Address:
Garba H Yunusa
Department of Radiology, Usmanu Danfodiyo University Teaching Hospital, Sokoto
Nigeria
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DOI: 10.4103/1118-8561.125559

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  Abstract 

Background: Helical computerized tomography (CT) has shown improved sensitivity and clinical utility as a diagnostic tool in the evaluation of patients presenting to the hospital with various abdominal conditions. This study assessed the various indications for this diagnostic tool and the CT findings in a tertiary health center. Materials and Methods: The study was conducted in the Department of Radiology of the Usmanu Danfodiyo University Teaching Hospital, Sokoto. Abdominal helical CT scans of patients referred to the department from the various clinical departments as well as the neighboring tertiary health centers were reviewed retrospectively. All the patients were scanned on Neusoft/Phillips C-3000 helical CT in the department following standard protocols for abdominal CT examinations. The patient demographics, clinical indications for the CT examination, CT findings, and provisional diagnoses were evaluated. Data was analyzed using SPSS version 17.0. Results: Thirty-five patients aged 1 to 78 years (mean ± SD; 46.6 ± 18.4) and made of 18 males and 17 females were studied. The most frequent indication for abdominal CT was in the 46-60 age group representing 34.3%, while the least number of indications were in the 1-15 and above 75-year age groups each constituting 8.6% and 5.7%, respectively. Suspected abdominal mass was the commonest indication constituting 28.6%, while further evaluation of known renal mass constituted 20% of the cases. Pancreatic, appendiceal, and bladder masses were among the commonest findings with prevalence of 20.3%, 8.7%, and 8.6%, respectively. Conclusions: Abdominal mass was the commonest indication for helical CT of the abdomen in this study, while pancreatic mass represented the commonest finding among the patients studied.

Keywords: Abdomen, computerized tomography, findings, helical, indications


How to cite this article:
Yunusa GH, Ma'aji SM, Saidu SA, Shamaki AM, Danfulani M. Helical computerized tomography of the abdomen: Indications and spectrum of findings in a tertiary health center. Sahel Med J 2013;16:154-9

How to cite this URL:
Yunusa GH, Ma'aji SM, Saidu SA, Shamaki AM, Danfulani M. Helical computerized tomography of the abdomen: Indications and spectrum of findings in a tertiary health center. Sahel Med J [serial online] 2013 [cited 2022 Jan 22];16:154-9. Available from: https://www.smjonline.org/text.asp?2013/16/4/154/125559


  Introduction Top


Computerized tomography (CT) is an X-ray diagnostic tool that offers easy and quick evaluation of the abdomen due to its high sensitivity, speed of acquisition, and multi-planar capability. [1],[2] Its speed and better tissue resolution when compared to ultrasonography or conventional plain radiography allows it to be used in the early evaluation of acute abdominal conditions such as diagnosis of acute appendicitis and localization of ureteric calculi. CT of the abdomen is also very useful in the evaluation of a wide range of abdominal conditions such as localization of abdominal masses, staging and re-staging of malignancies, and follow-up of patients post-operatively after various abdominal surgeries. [3] Undoubtedly, the need for conventional radiography has shown a gradual decline due to the increasing utility of helical CT in abdominal imaging. [4],[5],[6],[7],[8] This study evaluated the various indications for abdominal CT and its findings among 35 consecutive patients examined at the radiology department of the Usmanu Danfodiyo University Teaching Hospital, Sokoto.


  Materials and Methods Top


After obtaining the approval of our institution's Ethical Committee to perform this retrospective study, abdominal CT examination data of patients was retrieved from the archives of the Neusoft/Phillips C-3000 machine in the department of radiology. Thirty-five patients referred from the various clinical departments of the hospital as well as from the Federal Medical Centers in Birnin Kebbi and Gusau, Nigeria were examined with the CT scanner between December 2008 and February 2011. Patients were given oral contrast (3% gastrograffin; sodium and meglumine diatrizoate with iodine 370 mg/mL) before the study in order to outline the gastrointestinal tract and allow delineation of bowel loops from intra-abdominal masses. Patients were given intravenous contrast (76% urografin; sodium and meglumineamidotrizoate with iodine 370 mg/mL) after the initial acquisition of the native series in order to enhance lesion visualization and or characterization. Patients that had evidence of renal impairment, diabetes mellitus, and sickle cell disease were given a low-osmolar contrast medium iohexol (iopamiro) instead of urografin due to increased susceptibility to the nephrotoxicity of urografin. Patients with proven high creatinine levels were referred to the nephrologists for further assessment and dialysis before and after the CT examination. Dual phase imaging was used in the acquisition of the images for the evaluation of liver pathologies. [3],[9],[10] Timing of acquisition, variable slice thickness (5-10 mm), pitch (greater than 1), mAs, and Kv were optimized during the study in order to suit the diagnostic need of higher soft tissue contrast while keeping radiation dose to the patient as low as possible. [3] The CT volume images were analyzed on the operating console with the Neusoft software Dragon V3.1.1 of Neusoft and Phillips Systems Company limited that has various tools that allow thinner slice reconstruction (0.5 mm-3 mm), Multi-planar reformations (MPR), shaded surface display (SSD), and volume rendering (VR).

Indications for the CT abdomen were broadly classified as abdominal mass (where no clinical or sonographic specificity of a particular organ is established) or according to the abdominal viscera involved as evidenced by clinical, laboratory, and sonographic findings. Abdominal findings were characterized based on the location, size, density, presence or absence of contrast enhancement, and involvement of adjacent anatomical structures or organs. Other abnormal findings were also recorded.

Findings were analyzed with the Statistical Package for Social Sciences (SPSS) software version 17.0 (SPSS Inc. Chicago, IL, USA).


  Results Top


The age range of the patients was 1-78 years (mean ± SD; 46.6 ± 18.4 years). There were 18 males and 17 females. The most frequent indications for abdominal CT was in the 46-60 years age group representing 34.3%, while the least were in the 1-15 and above 75 years age groups each constituting 8.6% and 5.7%, respectively[Figure 1]. Abdominal and renal mass constituted 28.6% and 20% of indications for abdominal CT scan. Pancreatic, appendiceal, and bladder masses were among the most frequent findings with prevalence of 20.3%, 8.7%, and 8.6%, respectively, [Table 1].
Table 1: Indications for CT abdomen examination and sex distribution

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Figure 1: Bar chart showing the distribution of patients referred for CT abdomen by age group

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All the patients in the current study showed hypodense (hypoattenuating) hypoenhancing pancreatic lesions with associated dilatation of the main pancreatic duct [Figure 2]. One of the patients showed encasement of the portal vein as well as peripancreatic nodal enlargement. Four patients in the current study had pancreatic pseudocysts, which appeared as hypodense cystic pancreatic lesions with slightly contrast-enhancing walls.
Figure 2: CT of the abdomen showing a hypodense mass in the head of the pancreas. Oral contrast in the stomach is also seen

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Three of our patients had hepatic lesions, two of which were benign, while one was suspected to be malignant. A possible diagnosis of hydatid cyst was entertained in one of the patients that showed hypodense cystic non-enhancing lesion with calcifications. A primary liver cell carcinoma was considered when the CT showed multiple nodular hypodense hepatic masses, which showed mixed enhancing pattern as well as significant ascites.

Three renal masses were identified in this study, two of which were benign lesions consisting of perinephric abscess and multicystic kidney, while one had renal cell carcinoma (RCC) [Figure 3]. RCC was suspected based on the CT appearance of a mixed density (Hounsfield units, HU = 37-43) enhancing mass in the upper pole of the kidney with calcifications. Four cases of bladder masses were found in this study, and all were referred for further evaluation of the pelvis following inconclusive findings on abdomino-pelvic ultrasonography. The masses were hypodense and contrast-enhancing with areas of calcifications within them.
Figure 3: CT abdomen showing a large hypodense heterogeneous enhancing left renal mass. There is no extension beyond the renal capsule

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A total of 32 lesions were identified. No abnormality was seen on three of the CT examinations. The sizes of the lesions ranged from 9 mm (a ureteric calculus) to 348 mm (a mesenteric mass) measured in their widest transverse dimension. Of the 32 lesions identified, 21 (65.6%) were hypodense (hypoattenuating), 2 (6.3%) were hyperdense, while 9 (28.1%) lesions showed mixed density. Eight (25%) of the lesions showed no contras tenhancement, while 24 (75%) showed variable degree of contrast enhancement, which ranged from brilliant to peripheral rim of enhancement [Table 2]. Other findings included ascites, vascular invasion, calcifications, peritoneal fat stranding, and lymph node enlargement.
Table 2: Findings on contrast-enhanced CT of the abdomen

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All the three cases of appendiceal masses identified in our patients appeared as hypodense contrast-enhancing masses in the right iliac fossa with associated peritoneal fat stranding. Other findings amongst our patients included large mesenteric masses, uterine mass and non-specifically enlarged prostate and adrenal glands.


  Discussion Top


This study showed that helical CT of the abdomen could easily be used to determine the cause of abdominal pain or distension, characterize a known abdominal mass and stage malignancy. The low number of indications for the use of helical CT of the abdomen recorded in this study is related to a number of factors such as late presentation to the hospital, utilization of plain abdominal radiography and ultrasonography in the initial evaluation of acute abdomen as well as the high cost and out of pocket payment for CT scan in the setting where the study was done. The cost of the CT examination is surprisingly comparable or even higher than urgent abdominal exploratory laparotomy, thereby making it reasonable to consider the latter. [5]

Majority of the patients in this study presented with chronic abdominal conditions such as appendiceal, pancreatic, hepatic and renal masses, abdominal abscess, and pelvi-ureteric junction obstruction. The most common finding in this study was pancreatic masses, including pancreatic pseudocysts seen in 20.3% of the patients. This differs from the findings by Ismail et al. [11] who found a prevalence of 31.7% among patients referred for CT evaluation of intra-abdominal tumors.

There were equal number of males and females in the study. The highest number of indication for referral for abdominal CT among the female patients was abdominal mass, while the distributions of indications among the male patients were nearly equal [Table 1]. However, there is no apparent reason for the difference in this distribution. Majority of the patients referred fall in the middle age group of 46-60, which is about 34.3% of the patients. This is in concordance with the age group at higher risk of presenting with abdominal masses. [4],[6]

Multiphasic helical Multidetector CT is the imaging technique of choice in the evaluation of suspected pancreatic mass because of its ability to localize, characterize, determine vascularity, and help in local T staging of pancreatic cancers as well as determination of tumor resectability. [12],[13] On MDCT, pancreatic cancer appears as hypoenhancing mass with focal contour abnormality. The hypoenhancement is as a result of the desmoplastic and hypovascular nature of the tumor. It has been reported that in up to 10% of the cases, pancreatic cancer can be iso-attenuating to pancreatic parenchyma in which case, the secondary signs such as pancreatic ductal dilatation and parenchymal atrophy distal to the lesion with abrupt change in caliber at the site of the lesion provide clues to the diagnosis of pancreatic cancer. [14]

MDCT is about 90-95% accurate in diagnosing pancreatic cancer with reported positive predictive values of approximately 80% for tumor resectability. [12] In a study by Nishiharu et al., [15] which compared contrast-enhanced helical CT with breath-hold contrast-enhanced MR imaging for sensitivity in the detection of pancreatic adenocarcinoma and for accuracy in local tumor staging, it was shown that, thin-section CT is more sensitive than MR imaging for detection of peripancreatic and vascular invasion in patients with pancreatic cancer. Therefore, contrast-enhanced CT is considered to be the workhorse of pancreatic cancer staging.

The use of multiplanar reformatting has been shown to improve the detectability of small size pancreatic tumors, thereby improving the sensitivity of this test, [16],[17],[18] hence the utilization of MPR in the evaluation of the images during the review. Contrast material enhancement was optimized by employing the single and dual phase techniques in order to enhance lesion conspicuity and assessment of vascularity. [13],[16] Liver lesions were assessed in both the arterial and portal venous phases.

Dual-phase acquisition consisting of arterial and portal venous phases was used to evaluate the hepatic lesions in this study. Dual-phase helical CT has been shown to be the primary imaging modality that enables detection and characterization of focal liver lesions because it is an effective aid in determining the number, location, and nature of such lesions as well as in monitoring their change in size over time. [9],[10],[19],[20],[21] Report by Kamel et al. [19] has shown that dual-phase CT of the liver has a sensitivity of 69-71% and a high specificity of 86-91%, thereby enabling the detection and characterization of focal liver lesions.

Renal cell carcinoma is a hypervascular tumor, a feature that makes it demonstrate avid contrast enhancement in the corticomedullary-phase CT images. [22],[23],[24],[25],[26],[27],[28] Our patient also had intra-tumoral calcification, which is also a feature of RCC in up to 30% of the cases. [22],[23]

Ureteric calculi were found in a patient referred with history of recurrent renal colic that was technically difficult to localize by abdominal ultrasound and conventional intravenous urography (IVU) due to various limitations encountered during the use of these imaging modalities in the assessment of ureteric calculi. [2] Bowel gas and peritoneal fat limit visualization of the ureter on ultrasonography of the abdomen, except when it is markedly dilated.

CT offers the opportunity of assessing bladder wall, nodal involvement, mass effect on the ureters with consequent hydronephrosis and distant metastases, all of which ultrasonography alone can only partially demonstrate. [2]

While CT provides useful information regarding location, size, morphological characteristics of lesions, occasionally, there may be need to further evaluate indeterminate lesions with biopsy, additional laboratory tests or imaging including functional imaging for where available.

One of the limitations of this study was the lack of comparison of the CT findings with the final post-operative and or histopathological findings. Therefore, further studies incorporating the final histological diagnosis are encouraged.


  Conclusion Top


This study showed that abdominal mass was the commonest indication for helical CT of the abdomen, while pancreatic mass represented the commonest finding among the patients studied. Majority of the lesions were hypodense and showed variable pattern of contrast enhancement representing the pathological characteristic and or vascularity of the lesions. Appropriate use of helical CT of the abdomen, its multiplanar capability, and characterization of lesions as well as demonstration of other ancillary findings helps in establishing diagnosis and determining the course of patient management.

 
  References Top

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