From January 2009 to July 2012, all patients at our institution in whom MRCP was used to diagnose and classify the choledochal cysts were identified. Demographic information, clinical characteristics, and imaging details, and operative reports were collected for each patient. MRCP results were compared with intraoperative findings. ERCP’s if done, were also included and compared to the MRCP results.

Four commercially available MR imagers were used [Siemens 1.5-T Magnetom (Avanto), Siemens Magnetom 1.5 T (Symphony), Siemens Magnetom 1.5 T (Sonata), and Siemens 3-T Magnetom (Trio)]. MRCP imaging was performed using T2 weighted half-fourier acquisition single-shot turbo spin-echo (HASTE) sequences. Abnormal pancreaticobiliary ductal junction was diagnosed when the union between the common bile duct and pancreatic duct was located far from the duodenum and the length of common channel exceeded 15 mm in adults and more than 5 mm in pediatric patients.

All images were obtained using breath holding techniques except in one patient where non-breath-holding method (with respiratory triggering) was used. We obtained both sequential multislice imaging followed by maximum-intensity projection (MIP) reconstruction and single slice projection images.

The MRCP images were reviewed by a trained radiologist, with substantial experience reading MRCPs. The radiologist had no knowledge of the patients’ presentation or clinical data. Relevant findings included pancreaticobiliary junction, common channel, and pancreatic duct location, choledochal cyst type and characterization, and additional gallbladder pathology. All MRCP findings were compared with intraoperative and ERCP findings. However, secretin stimulation test was not performed at our center.

The English language literature was searched to identify relevant studies. PubMed, Google Scholar and Scopus, were searched using the keywords “MRCP” and “choledochal cyst”. Reference lists of all retrieved articles were further reviewed, and inclusion/exclusion criteria were applied to identify the potentially relevant studies. Studies were included that had a minimum of 5 patients in whom MRCP was used as a diagnostic tool and findings were compared to ERCP or surgery. Smaller case series were excluded, as is consistent with previously published peer-reviewed data[23,24].

This study was approved by the local institutional review board.

Subsequently, the patients underwent MRCP as their primary preoperative diagnostic study. Six patients had type IV and 1 patient had type I according to the Todani classification scheme[25]. One patient had a new variant of choledochal cyst with confluent dilatation of the CBD and cystic duct. In every case except for one, ultrasound (US) and CT findings were the same as those seen on MRCP. Patient 3 was found to have type I cyst on US, but was shown to have type IV on MRCP. All MRCP reads were confirmed intraoperatively.

Seven of the patients had APBJ. Three patients had long common channel, while four were classified based on their acute angle of union. MRCP also detected gallbladder stones in 2 patients, a CBD stone in 1 patient and a pancreatic duct stone in one patient. All findings were later confirmed surgically except in a patient with choledocholithiasis where ERCP was also done (Figures 1-4).

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Figure 1 Sixty-year-old female. A, B: Coronal and axial T2 weighted half-fourier acquisition single-shot turbo spin-echo images show a type IV Choledochal cyst; C: Thin-slice magnetic resonance cholangiopancreatography sequence demonstrates the anomalous union of pancreaticobiliary duct (arrow).

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Figure 2 Forty nine-year-old male. Maximum intensity projection reconstruction of thin-slice magnetic resonance cholangiopancreatography half-fourier acquisition single-shot turbo spin-echo images demonstrates a choledochal cyst type IV. Note the anomalous union of the pancreaticobiliary duct (black arrow) and the presence of a small stones in the pancreatic duct (arrows).

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Figure 3 Seventy four-year-old female. Axial and coronal T2 weighted half-fourier acquisition single-shot turbo spin-echo images showing type IV choledochal cyst with multiple stones in the lumen.

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Figure 4 Forty seven-year-old male. A, B: Coronal T2 weighted half-fourier acquisition single-shot turbo spin-echo image and thick-slice magnetic resonance cholangiopancreatography sequence; C: Maximum intensity projection reconstruction demonstrate a choledochal cyst type IV.

Surgical resection of choledochal cysts was performed in all the patients. The types of resection were choledochal cyst excision with roux-en-y hepaticojejunostomy, cyst excision with Hutson-Russell loop, and hepatic segmentectomy and cholecystectomy with roux-en-y hepaticojejunostomy.

Over the past decade, MRCP has started to replace ERCP as the diagnostic study of choice for a variety of biliary and pancreatic conditions[35-41]. Specifically, MRCP has been reported to have similar diagnostic accuracy for extrahepatic biliary diseases such as choledocholithiasis and biliary malignancies[40,42]. A similar trend is notable with respect to choledochal cysts. Initially, MRCP was extremely limited in its diagnostic accuracy and used sparingly in extremely cooperative patients. The advent of respiratory trigger and non-breath holding techniques gradually enabled MRCP use in less cooperative patients, especially children[43-46]. Concurrently, rapid imaging techniques including HASTE/single-shot FSE/single-shot turbo spin echo (TSE) decreased image acquisition time to 2-5 s. Today, MRCP is utilized to study the biliary system in almost all populations[47,48].

ERCP is the definitive diagnostic method for evaluating choledochal cysts and ABPJ, but the procedure comes with inherent risks (Table 2). ERCP is invasive and requires sedation in all patients. For pediatric patients and those with low respiratory reserve, general anesthesia is required. Morbidity from ERCP ranges from 2%-8% in children and 1%-2% in adults, which rises to 10% when combined with sphincterotomy, and mortality estimates is estimated between 0.05%-0.90%[42,49-53]. Cholangitis, duodenal perforation, hemorrhage, contrast allergy, biliary sepsis, and pancreatitis are all recognized complications. Even without untoward complications, complete pancreatico-biliary opacification fails in 5%-30% of patients[54]. Incompletely visualizing the pancreaticobiliary duct union, or potentially missing a small CBD stone or cancer can impact operative intervention and results. Hence, the interest in the MRCP as a less invasive, less morbid diagnostic and preoperative modality has increased.

A total of 19 published studies including our case-series on adult and pediatric patients met criteria for inclusion in the review. The study populations and methodologies did vary somewhat. While ten studies were devoted to children exclusively, nine case-series evaluated MRCP in all ages. Fourteen studies were retrospective, and five were prospectively designed. Since the studies spanned a 17-year period, the MRCP technology has evolved, and a range of image acquisition techniques were employed. However, all studies compared and rated MRCP findings with at least one more established diagnostic modality.

MRCP demonstrated excellent overall detection rate for choledochal cysts, albeit with some specific limitations. Out of 368 patients (age range 6 d-78 years old), the range for choledochal cyst detection rate was 96%-100% (Table 3). Of note, all 3 false negatives were reported in a single study[55] with all 3 undetected cases being exclusively type III, choledochocele. Only 10 of the 19 studies specified the choledochal cysts’ Todani classification[25]. Range for detection rates was 81%-100% for type  I, 100% for type II, 84%-100% for type IV, and 100% for type V. Type III’ slower detection rate was reported only in one study (73%)[55] is likely due to its location near the ampulla, and perhaps because a small choledochocele may become evident only when contrast medium is injected under pressure[67]. Kamisawa et al[68] also suggested the use of 3 dimensional MRCP and dynamic MRCP with secretin stimulation for congenital pancreaticobiliary malformations especially choledochocele.

Our review also assessed MRCP’s ability to detect APBJ in the setting of a choledochal cyst (Table 4). Fifteen studies provided information about APBJ detection, providing a total of 223 cases. MRCP diagnosis of APBJ yielded a sensitivity of 53%-100%, specificity of 90%-100%, and overall diagnostic accuracy of 56%-100%. In contrast, ERCP has been reported with sensitivity and specificity > 90% for diagnosing APBJ[11]. Possible explanations for these differences variation include the broad range of patient ages and heterogeneous imaging techniques used across studies. Choledochal cyst size and concurrent impacted stones may limit MRCP’s sensitivity[48,56]. Furthermore, MRCP does not distend the bile ducts, leading to a suboptimal representation of the pancreaticobiliary junction[69]. Newer imaging sequences, such as secretin-enhanced MRCP[56,70], 3D SSFSE[39], HASTE sequence single-slice, and MIP images[31,71], all have increased diagnostic accuracy in adults and pediatric patients.

Choledochal cysts and ABPJ aside, we also evaluated MRCP’s ability to visualize clinically related biliary pathology in patients diagnosed with CC’s. MRCP detected choledocholithiasis in nearly all studies (Table 5), and 87% (13/15) of reported cholangiocarcinomas in this cohort[55]. MRCP images are helpful when detecting cholangiocarcinomas because they display periductal anatomy, a critical element in surgical decision-making[55,72]. Previous studies support using MRCP for this purpose[40,56,73]. Irie et al[56] recommended MRCP axial plane images in detecting concurrent choledocholithiasis, especially in the common channel. Following cyst excision, MRCP may also play a role in surveillance for the subsequent development of cholangiocarcinoma[74-77].

This study is subject to certain limitations. First, the cases presented represent a small number of patients from our local institution, and they were treated according to our own practices and protocols. They may not represent other patients in other institution. Moreover, some caution is necessary in interpreting findings from our literature review. The studies that were included span 15 years, employing different designs, techniques, and gold standards as imaging and detection protocols have evolved. Due to those improvements, contemporary detection rates are possibly higher than what our cumulative data indicates.

In conclusion, our retrospective study and review of relevant literature suggest that MRCP is as effective as an initial pre-operative diagnostic study for choledochal cysts in adult and pediatric populations. In addition, MRCP is equivalent to ERCP in determining choledochal cyst type, and helpful in diagnosing related pancreaticobiliary anomalies, such as ABPJ, cholangiocarcinoma, and choledocholithiasis. Given its relatively moderate risk profile and lower cost, MRCP should be the diagnostic test of choice when pre-operatively evaluating choledochal cysts and their associated anomalies. But more evaluation needs to be done to assess the MRCP ability to detect APBJ and choledochocele. ERCP should be used when MRCP inadequately visualizes the terminal CBD or the pancreaticobiliary duct junction, or when a therapeutic procedure is anticipated.

Choledochal cysts carry a long term morbidity and mortality. Choledochal cysts are frequently associated with various anatomic variants that carry considerable risk of complications such as cholangiocarcinoma. Therefore outlining these anatomic details are critical in order to help surgeons plan their operations and prevent complications.

Various techniques like ultrasound, computed tomography, radionuclide scintigraphy and endoscopic retrograde cholangiopancreatography (ERCP) are used to visualize choledochal cyst and their anatomic variants. However magnetic resonance cholangiopancreatography (MRCP) has received increasing attention as the primary diagnostic study. This study presents our institution’s experience using MRCP to diagnose choledochal cysts. A literature review on the topic accompanies the results.

This is the first study which review the literature from past 16 years explaining MRCP as primary diagnostic approach in adult and pediatric patients for choledochal cysts. Authors report the advancement of MRCP with time. It shows how newer imaging techniques have improved diagnostic accuracy of MRCP.

MRCP being lower cost and noninvasive should be diagnostic test of choice used pre-operatively for choledochal cysts and their associated anomalies. ERCP should be used when MRCP inadequately visualizes the terminal common bile duct or the pancreaticobiliary junction or when a therapeutic procedure is needed.

Half-fourier acquisition single-shot turbo spin-echo (HASTE) refers to a rapid magnetic resonance imaging protocol with an image acquisition time of 2-5 s. HASTE has increased the diagnostic accuracy of MRCP in both adult and pediatric patients.

This article deals with new diagnostic approach for choledochal cysts. The results are interesting and suggest that after initial ultrasound and computed tomography scan, MRCP should be the next diagnostic test in both adult and pediatric patients. ERCP should be reserved for patients where therapeutic intervention is needed.