Imaging evaluation of the biliary tree includes ultrasound, CT, CT cholangiography with a biliary contrast agent, MRCP, ERCP, and PTC. Both ultrasound and MRCP do not imply an ionizing radiation. Both do not utilize contrast agents. Sonography is not superior to evaluate the main biliary tract, with a reported sensitivity ranging from 20 to 80%, at biliary stone detection .
Though MRCP is a reliable non-invasive technique, its use is hindered in those with pacemakers or aneurysm clips and those who are claustrophobic .
ERCP has the privilege of providing diagnostic and therapeutic intervention in the same session (endoscopic sphincterotomy, stone extraction, and endoscopic guided biopsy). However, it yields a little information about solid abdominal organs, is invasive as well, and poses a 0.5–5.0% complication rate (diverse reaction to sedatives, cardio-respiratory dysfunction, pancreatitis, perforation of the gut, bleeding, cholangitis, sepsis, and death) .
MDCT pre-contrast series is useful in those with an elevated bilirubin level or abnormal liver or renal functions. By using CPR/MPR, all intra-hepatic ducts can be viewed, a feature that is not possible at ERCP or PTC. Contrast series data set is used as well to reproduce angiography images to delineate tumoral vascular invasion . MDCT cholangiography assesses globally the biliary obstruction regarding the biliary tree, vessels, and solid abdominal organs (liver, pancreas, and duodenum), a feature that does not exist at ERCP and PTC [29, 30].
In our series, all our patients were complaining of yellowish discoloration of the skin and sclera as the most common clinical complaint presented in all patients except for 6 cases. Our result agrees with Mathew et al. .
In this study, MDCT identified the level of biliary obstruction in 69 patients with 100% accuracy which agreed with Mohamed et al. .
Our study showed a higher prevalence for male affection to biliary obstruction than for females by 56.5 to 43.5%. Rishi et al.  showed different prevalence which is equal to male to female affection.
Regarding the most affected age group, our study showed that 60–70 years is the most affected group, while Rishi et al.  stated that the majority of cases are in the age group 41–60 years.
Moderate degree of biliary duct dilatation initiated by malignant sources was more severe (41.5%) than that of benign sources (21.4%), findings similar to the findings of Mohamed et al. .
In our study, it was found that calcular obstructive jaundice was the main cause of benign OJ (24.6%); these were as those of Mathew et al.  who showed calcular cause was responsible for 22% of cases of biliary obstruction.
Regarding the nature of the cause of biliary obstruction, our study showed malignant dominance by 59.4% compared to 40.6% for benign which agrees with Narayanaswamy et al.  which showed 66.7% for malignancy while 33.3 for benign causes. But Mathew et al.  stated benign causes were 56% while malignant was only 44%.
Malignant stricture was identified by MDCT in 36 cases; 34 cases were confirmed by standard examination; a case had a slight left-sided intrahepatic dilatation with hyper-enhancement of the duct wall and abrupt duct narrowing, identified as cholangiocarcinoma. ERCP identification was acute cholangitis. The second case was a well-known case of colon cancer on follow-up, a hepatic focal lesion identified as necrotic metastasis but cytology confirmed an abscess. Alternatively, a case of metastatic portahepatis LN was confirmed to be cholangiocarcinoma.
The SN, SP, PPV, NPV, and ACC of MDCT cholangiography in the detection of malignant stricture were 94.4%, 93.94, 94.44%, 93.93%, and 94.2%, respectively, that come to an agreement with Mohamed et al.  which the results were 96.8%, 94.9, 98.2%, 96.7%, and 95.6%.
In our series, pancreatic carcinoma is present in 14 patients responsible for 20.3% of the total cases; in the study of Mohamed et al. , pancreatic carcinoma was responsible for 17.8% of the causes of biliary obstruction. Mathew et al.  claimed that it affected 20% of cases. MDCT identified all the cases of pancreatic carcinoma with 100% accuracy. Most studies agree with the basis of diagnosing as ours: a hypodense mass relative to enhanced pancreatic tissue that may show faint peripheral enhancement.
In other malignancies, there were 5 cases, 3 cases diagnosed as hepatic focal lesion, 1 case as GB carcinoma and gastric carcinoma, and one case was wrongly diagnosed as metastatic focal lesion but proven as an abscess. Mohamed et al.’s  results included 8 cases of intrahepatic malignant masses, one case was diagnosed as benign stricture but pathologically proven to be metastasis from non-Hodgkin lymphoma. Tummala et al.  reported extrinsic compression by focal lesion adjacent to the bile duct in 3.2% of their patients (compared to 4.3% in our study).
Periampullary carcinoma was found in 3 cases, all were proven pathologically to be periampullary carcinoma; it represented 4.3% of the cases. Mohamed et al.  showed a higher affection rate (14%) with 100% accuracy that agreed with our results while Narayanaswamy et al.  was 96%.
Calcular etiology was diagnosed in 17 cases, 1 case was diagnosed by MDCT as calcular but proven to be a benign stricture (sludge) and another case which was diagnosed by MDCT as negative (no detected cause) proven to be a black cholesterol stone that was not visible. It was the most common cause of benign biliary obstruction in our study by contributing to 24.6% of the cases with SN 94.1%, SP 98%, PPV 94.1%, NPV 98% and, ACC 97.1%. Our results agree with Rishi et al.  that revealed in their study ACC of MDCT in the detection of choledocholithiasis is 98%, SN of 100%, and SP of 97.4% showed also was the most frequently diagnosed cause of obstruction by 24%. You et al.  mentioned intraductal high attenuating focal lesions were detected in enhanced or unenhanced scans subsequent to the course of CBD as criteria for diagnosis which agreed with our findings.
Four patients with post-operative iatrogenic bile duct injury were included which represented 5.8% of the total causes. Heller et al.  imply that iatrogenic is the second most common reason for benign biliary tract strictures after calcular which agreed with ours. The study showed free fluid in most cases which was noted in the abdomen accompanying fluid at the GB bed. MDCT diagnosed all the patients correctly based on the history and findings making statistical measures for the diagnostic performance of MDCT in detecting bile duct injury as follows: SN 100%, SP 100%, PPV 100%, NPV 100%, and ACC 100%. El-gerby et al.  and Meng et al.’s  results showed the same SN, SP, PPV, NPV, and ACC as ours for biliary leakage detection.
Four patients had portahepatis lesions in our study. It contributed by 5.8% of the causes which showed different results from Mohamed et al.  which was 4.4% only. Two cases were diagnosed as lymphoma involving portahepatis LN and other two cases as malignant metastatic portahepatis LN. Rishi et al.  stated that lymphoma represented 6% of the causes of obstruction compared to 2.9% in our study and 100% ACC in detecting lymphoma which was the same finding as Mathew et al. . Our diagnostic performance was as follows: SN 100%, SP 98.48%, PPV 75%, NPV 100%, and ACC 98.55%.
Benign stricture was diagnosed by MDCT in three cases; two cases were proven to be due to recurrent cholangitis which agrees with Heller et al.  who stated cholangitis is considered one of the commonest causes of benign strictures. Mohamed et al.  mentioned the MDCT criterion for identifying a benign stricture which includes a smooth and gradually elongated narrowing of CBD in a short section measuring less than 1 cm without the presence of a mass. Our diagnostic performance for the detection of the benign strictures was as follows: SN 40%, SP 98.44%, PPV 66.67%, NPV 95.45%, and ACC 94.20%. Mohamed et al.’s  statistical results were SN 66.7%, SP 80.2%, PPV 80.2%, NPV 91.7%, and ACC 92.6% which were near to our results except for sensitivity as one case was diagnosed by MDCT as benign stricture proven by biopsy as a small cholangiocarcinoma, while Mathew et al.  showed higher percentages as follows: SN 100%, SP 97.8%, PPV 83.3%, NPV 100%, and ACC 98%.
Inflammatory was diagnosed by MDCT in three cases, two cases were due to acute pancreatitis and one case was due to acute cholecystitis. Patel et al.  stated that acute cholecystitis diagnosis is confirmed in the presence of GB wall thickening, GB distention peri-cholecystic fluid, inflammatory stranding and sub-serosal edema which agreed with our findings. Bonheur et al.  mentioned that biliary obstruction can occur from external compression of the bile duct due to inflammation as pancreatitis or cholecystitis. Bollen , also mentioned that acute pancreatitis could lead to biliary complications including biliary obstruction.
Our study showed 100% SN, SP, PPV, NPV, and ACC regarding the results of inflammatory causes. Mathew et al.’s  study results presented that the inflammatory cause of biliary obstruction has SN, SP, PPV, NPV, and ACC of 100% which in turn agrees with our results.
A 13-year-old female case with a cystic dilated segment involving extrahepatic biliary tree was diagnosed as congenital choledocal cyst type IA. Our study showed 100% SN, SP, PPV, NPV, and ACC to diagnose congenital biliary obstruction. Mathew et al.’s  study results showed choledocal cyst has SN, SP, PPV, NPV, and ACC of 100% which agrees with our results.
One of the limitations of this work includes the small number of cases, particularly in the benign stricture group. The main limitations of the use of intravenous agents are the relatively high rate of allergic reactions and the risk of renal and/or hepatic toxicity so patients with biliary obstruction and high renal functions could not be assessed and risk of radiation and anesthesia for young patients.