Mild autonomous cortisol secretion in adrenal incidentalomas and risk of fragility fractures: a large cross-sectional study.

OBJECTIVE: Mild autonomous cortisol secretion (MACS) has been associated with a higher prevalence of osteoporosis, although most data rely on single-center studies with limited sample size. We aimed to assess the prevalence of fragility fractures and contributing factors in a large cohort of patients with adrenal incidentalomas. DESIGN AND METHODS: Medical records of 1023 patients with adrenal incidentalomas from 1990 to 2019 were reviewed, and 735 patients were selected. Clinically obtained electronic radiological images closest to first endocrine evaluation, such as lateral views of spine X-rays or CT thoraco-abdominal scans, were reviewed to screen for asymptomatic morphometric vertebral fractures. Clinical fragility fractures, hormonal, and dual-energy x-ray absorptiometry (DXA) indices were also recorded. RESULTS: Four hundred seventy-four patients had nonfunctioning (NF) adrenal incidentalomas, 238 had MACS and 23 adrenal Cushing's syndrome (AC). Prevalence of fragility fractures was different (P = .018) between groups, respectively, 24.1% (NF), 34.0% (MACS), and 30.4% (AC), with significant difference between NF and MACS (P = .012). When analyzed separately by sex and menopausal status, this difference remained significant in postmenopausal women (P = .011), with a fracture prevalence of 22.2% (NF) and 34.6% (MACS). Fracture prevalence was similar in males. Women with MACS aged ≥65 years reported a 48.8% prevalence of fractures, as compared with 29.5% in NF (P < .01). In postmenopausal women, fragility fractures were associated with age (odds ratio [OR] 1.1, P < .001), smoking (OR 1.8, P = .048), and 1 mg-dexamethasone suppression test (DST) cortisol (OR 3.1, P = .029), while in men, only age was associated with fragility fractures. CONCLUSIONS: A considerable fracture burden was shown in postmenopausal women with adrenal incidentalomas and MACS, with clinical implications for the evaluation and management of bone metabolism.

Association between anatomic variations of extrahepatic and intrahepatic bile ducts: Do look up!

Biliary anatomic variations are usually asymptomatic, but they may cause problems in diagnostic investigations and interventional and surgical procedures, increasing both their technical difficulty and their postoperative complication rates. The aim of the present study was to evaluate the prevalence of anatomic variations in the intrahepatic biliary ducts (IHBD) in relation to demographical and clinical characteristics in a large study population requiring magnetic resonance cholangiopancreatography (MRCP) for various clinical conditions. The possible association between IHBD and extrahepatic biliary ducts (EHBD) variants was then explored. From January 2017 to May 2019, 1004 patients underwent MRCP. Demographical and clinical data were collected. IHBD and EHBD anatomy were recorded and the EHBD anatomy was classified using both qualitative and quantitative classifications. The presence of a type 3 EHBD variant (an abnormal proximal cystic duct [CD] insertion) in both qualitative and quantitative classifications and an intrapancreatic CD were associated with the presence of IHBD variants at univariate analysis (p = 0.008, p = 0.019, and p = 0.001, respectively). The presence of a posterior or medial insertion of the CD into the EHBD was a strong predictive factor of the presence of IHBD variants both at uni- and multivariate analysis (p = 0.002 and p = 0.003 for posterior insertion and p = 0.002 and p = 0.002 for medial insertion, respectively). The presence of gallstones on MRCP resulted in a strong predictor of the presence of an anatomical variant of the IHBD both at uni- and multivariate analysis (p = 0.027 and p = 0.046, respectively). In conclusion, the presence of a type 3 variant of the EHBD, an intrapancreatic CD and, especially, a posterior/medial CD insertion into the EHBD represent predictive factors of the concomitant presence of IHBD variants, thus radiologists must be vigilant when encountering these EHBD configurations and always remember to "look up" at the IHBD. Finally, the presence of an IHBD variant is a strong predictive factor of gallstones.

Co-Infections and Superinfections in COVID-19 Critically Ill Patients Are Associated with CT Imaging Abnormalities and the Worst Outcomes.

Background: Bacterial and fungal co-infections and superinfections have a critical role in the outcome of the COVID-19 patients admitted to the Intensive Care Unit (ICU). Methods: The present study is a retrospective analysis of 95 patients admitted to the ICU for COVID-19-related ARDS during the first (February−May 2020) and second waves of the pandemic (October 2020−January 2021). Demographic and clinical data, CT imaging features, and pulmonary and extra-pulmonary complications were recorded, as well as the temporal evolution of CT findings when more than one scan was available. The presence of co-infections and superinfections was registered, reporting the culprit pathogens and the specimen type for culture. A comparison between patients with and without bacterial and/or co-infections/superinfections was performed. Results: Sixty-three patients (66.3%) developed at least one confirmed co-infection/superinfection, with 52 (82.5%) developing pneumonia and 43 (68.3%) bloodstream infection. Gram-negative bacteria were the most common co-pathogens identified and Aspergillus spp. was the most frequent pulmonary microorganism. Consolidations, cavitations, and bronchiectasis were significantly associated with the presence of co-infections/superinfections (p = 0.009, p = 0.010 and p = 0.009, respectively); when considering only patients with pulmonary co-pathogens, only consolidations remained statistically significative (p = 0.004). Invasive pulmonary aspergillosis was significantly associated with the presence of cavitations and bronchiectasis (p < 0.001). Patients with co-infections/superinfections presented a significantly higher mortality rate compared to patients with COVID-19 only (52.4% vs. 25%, p = 0.016). Conclusions: Bacterial and fungal co-infections and superinfections are frequent in COVID-19 patients admitted to ICU and are associated with worse outcomes. Imaging plays an important role in monitoring critically ill COVID-19 patients and may help detect these complications, suggesting further laboratory investigations.

An Imaging Overview of COVID-19 ARDS in ICU Patients and Its Complications: A Pictorial Review.

A significant proportion of patients with COVID-19 pneumonia could develop acute respiratory distress syndrome (ARDS), thus requiring mechanical ventilation, and resulting in a high rate of intensive care unit (ICU) admission. Several complications can arise during an ICU stay, from both COVID-19 infection and the respiratory supporting system, including barotraumas (pneumothorax and pneumomediastinum), superimposed pneumonia, coagulation disorders (pulmonary embolism, venous thromboembolism, hemorrhages and acute ischemic stroke), abdominal involvement (acute mesenteric ischemia, pancreatitis and acute kidney injury) and sarcopenia. Imaging plays a pivotal role in the detection and monitoring of ICU complications and is expanding even to prognosis prediction. The present pictorial review describes the clinicopathological and radiological findings of COVID-19 ARDS in ICU patients and discusses the imaging features of complications related to invasive ventilation support, as well as those of COVID-19 itself in this particularly fragile population. Radiologists need to be familiar with COVID-19's possible extra-pulmonary complications and, through reliable and constant monitoring, guide therapeutic decisions. Moreover, as more research is pursued and the pathophysiology of COVID-19 is increasingly understood, the role of imaging must evolve accordingly, expanding from the diagnosis and subsequent management of patients to prognosis prediction.

Association Between Aldosterone and Parathyroid Hormone Levels in Patients With Adrenocortical Tumors.

OBJECTIVE: Patients with primary aldosteronism (PA) can present with high PTH levels and negative calcium balance, with some studies speculating that aldosterone could directly stimulate PTH secretion. Either adrenalectomy or mineralocorticoid receptor blockers could reduce PTH levels in patients with PA. The aim of this study was to assess the relationship between aldosterone levels and parathyroid hormone (PTH)-vitamin D-calcium axis in a cohort of patients with PA, compared with patients with nonsecreting adrenocortical tumors in conditions of vitamin D sufficiency. METHODS: We enrolled a series of 243 patients retrospectively, of whom 66 had PA and 177 had nonsecreting adrenal tumors, and selected those with full mineral metabolism evaluation and 25(OH) vitamin D levels >20 ng/mL at the time of initial endocrine screening. The final cohort was composed of 26 patients with PA and 39 patients, used as controls, with nonsecreting adrenal tumors. The relationships between aldosterone, PTH levels, and biochemistries of mineral metabolism were assessed. RESULTS: Aldosterone was positively associated with PTH levels (r = 0.260, P < .05) in the whole cohort and in the PA cohort alone (r = 0.450; P = .02). In the multivariate analysis, both aldosterone concentrations and urinary calcium excretion were significantly related to PTH levels, with no effect of 25(OH) vitamin D or other parameters of bone metabolism. CONCLUSION: PTH level is associated with aldosterone, probably independent of 25(OH) vitamin D levels and urinary calcium. Whether aldosterone interacts directly with the parathyroid glands remains to be established.

Comparing the first and the second waves of COVID-19 in Italy: differences in epidemiological features and CT findings using a semi-quantitative score.

PURPOSE: CT findings of hospitalized COVID-19 patients were analyzed during both the first and the second waves of the pandemic, in order to detect any significant differences between the two groups. METHODS: In this observational, retrospective, monocentric study, all hospitalized patients who underwent CT for suspected COVID-19 pneumonia from February 27 to March 27, 2020 (first wave) and from October 26 to November 24, 2020 (second wave) were enrolled. Epidemiological data, radiological pattern according to the RSNA consensus statement and visual score extension using a semi-quantitative score were compared. RESULTS: Two hundred and eleven patients (mean age, 64.52 years ± 15.14, 144 males) were evaluated during the first wave while 455 patients (mean age, 68.26 years ± 16.34, 283 males) were studied during the second wave. The same prevalence of patterns was documented in both the first and the second waves (p = 0.916), with non-typical patterns always more frequently observed in elderly patients, especially the "indeterminate" pattern. Compared to those infected during the first wave, the patients of the second wave were older (64.52 vs.68.26, p = 0.005) and presented a slightly higher mean semi-quantitative score (9.0 ± 2.88 vs. 8.4 ± 3.06, p = 0.042). Age and semi-quantitative score showed a positive correlation (r = 0.15, p = 0.001). CONCLUSIONS: There was no difference regarding CT pattern prevalence between the first and the second waves, confirming both the validity of the RSNA consensus and the most frequent radiological COVID-19 features. Non-typical COVID-19 features were more frequently observed in older patients, thus should not be underestimated in the elderly population.

Expected and non-expected immune-related adverse events detectable by CT.

PURPOSE: Cancer treatments with immune checkpoint inhibitors (ICI) are associated with a unique set of drug toxicities called immune-related adverse events (irAES). The aim of the present study was to describe the radiological manifestation of irAES detectable by CT. METHOD: Retrospective analysis of 284 patients treated with ICI for various types of advanced cancer; of them, 129 patients were selected, all having been treated with single-agent ICI, and all with a baseline CT scan and follow-up scans available at our Institute. CT examinations were reviewed by two radiologists involved in the study with a consensus reading. Imaging findings consistent with irAES were reported and correlated with clinical-laboratory data. RESULTS: Immune-related adverse events were found in 25/129 (19.4 %) patients. No statistically significant differences were found in either the prevalence of irAES or in the time of onset of tumour type. Thoracic complications were detected in 14/25 (56.0 %) patients consisting in: 3 radiation recall pneumonia, 3 Transient Asymptomatic Pulmonary Opacities (TAPOs), 3 hypersensitivity pneumonia, 2 diffuse alveolar damage, 2 organizing pneumonia, 1 sarcoid-like reaction. In the remaining 11/25 (44.0 %), there were extra-pulmonary complications: 3 colitis, 4 cholecystitis, 2 pancreatitis and 2 cases of visceral ischemia. CONCLUSIONS: Radiologists should be aware of the wide spectrum of irAES as they could affect the outcome. Pneumonia is the most frequent irAES; however, the international classification for interstitial lung disease does not seem to be capable of describing all possible drug-related pulmonary toxicities. Additional findings included TAPOs, radiation recall pneumonia and sarcoid-like reaction.

Imaging-based diagnosis of benign lesions and pseudolesions in the cirrhotic liver.

Liver cirrhosis is a leading cause of death worldwide, with 1-year mortality rates of up to 57% in decompensated patients. Hepatocellular carcinoma (HCC) is the most common primary tumor in cirrhotic livers and the second leading cause of cancer-related mortality worldwide. Annually, up to 8% of patients with cirrhosis develop HCC. The diagnosis of HCC rarely requires histological confirmation: in fact, according to the most recent guidelines, the imaging features of HCC are almost always sufficient for a certain diagnosis. Thus, the role of the radiologist is pivotal because the accurate detection and characterization of focal liver lesions in patients with cirrhosis are essential in improving clinical outcomes. Despite recent technical innovations in liver imaging, several issues remain for radiologists regarding the differentiation of HCC from other hepatic lesions, particularly benign lesions and pseudolesions. It is important to avoid misdiagnosis of benign liver lesions as HCC (false-positive cases) because this diagnostic misinterpretation may lead to ineligibility of a patient for potentially curative treatments or inappropriate assignment of high priority scores to patients on waiting lists for liver transplantation. This review presents a pocket guide that could be useful for the radiologist in the diagnosis of benign lesions and pseudolesions in cirrhotic livers, highlighting the imaging features that help in making the correct diagnosis of macroregenerative nodules; siderotic nodules; arterioportal shunts; hemangiomas, including fast-filling hemangiomas, hemangiomas with pseudowashout, and sclerosed hemangiomas; confluent fibrosis; pseudomasses in chronic portal vein thrombosis; and focal fatty changes.

A New Quantitative Classification of the Extrahepatic Biliary Tract Related to Cystic Duct Implantation.

BACKGROUND: Knowledge regarding biliary anatomy and its variations, including the cystic duct (CD), is important in the pre-surgical setting and for predicting biliary diseases. However, no large series has focused on CD evaluation using a quantitative analysis. The primary aim of this prospective study was to create a 'taxonomic' classification of CD anatomy in a large cohort of subjects who underwent magnetic resonance cholangiopancreatography (MRCP). The secondary aim was to evaluate the correlations between extrahepatic bile duct (EHBD) variants and biliary diseases. METHODS: We enrolled patients who underwent MRCP for different clinical indications from January 2017 to May 2019. Demographical, anatomical and clinical data were evaluated using statistical analyses, as appropriate. The anatomical assessment of EHBD was performed using the standard classification for CD in low, medium, and high insertions, and the lengths of CD to the duodenal papilla (DP), and EHBD was determined to conduct a new quantitative analysis. RESULTS: The final study population comprised 1004 subjects. A new classification for EHBD as per the percentile distribution of the ratio CDDP/EHBD was designed, and the following categories were obtained: type 1 (below the 25th percentile) for CDDP/EHBD ratio ≤ 50%; type 2 (25th to 75th percentile) for CDDP/EHBD ratio 51-75% and type 3 (above the 75th percentiles) for CDDP/EHBD ratio > 75%. Type 1 of the new classification of CD implantation was significantly superior in terms of the detection of low, medial and intra-pancreatic CD that was significantly correlated with a high risk of choledochal lithiasis in comparison with the standard classification (P < 0.001). CONCLUSIONS: The new classification of CD implantation enables identification of the vast majority of intra-pancreatic CDs that are correlated with a high risk of choledochal lithiasis in a single category (type 1) that is easy to identify using imaging.

Prevalence and Incidence of Atrial Fibrillation in a Large Cohort of Adrenal Incidentalomas: A Long-Term Study.

CONTEXT: Chronic glucocorticoids excess leads to morphological and functional cardiac alterations, a substrate for arrhythmias. Autonomous cortisol secretion (ACS) in adrenal incidentalomas is a model of chronic endogenous hypercortisolism. OBJECTIVE: To investigate prevalence and incidence of atrial fibrillation (AF) in a large cohort of patients with ACS. DESIGN: Retrospective study. SETTING: University hospital. PATIENTS: Patients evaluated between 1990 and 2018 for adrenal incidentalomas (n = 632), without pheochromocytoma, primary aldosteronism, Cushing syndrome, congenital adrenal hyperplasia, and adrenal malignancy. Cortisol after 1-mg dexamethasone suppression test < or > 50 nmol/L defined nonsecreting tumors (NST) (n = 420) and ACS (n = 212), respectively. INTERVENTION: Assessment of AF at baseline (n = 632) and during a median follow-up of 7.7 years retrospectively (NST, n = 249; ACS, n = 108). Comparison with general population. MAIN OUTCOME MEASURE: Prevalence and incidence of AF. RESULTS: AF prevalence was higher in patients with ACS (8.5%) than NST (3.1%, P = 0.003) and the general population (1.7%; P < 0.001 vs ACS, P = 0.034 vs NST). The age-adjusted rate ratio to the general population was 1.0 for NST and 2.6 for ACS. AF was associated with ACS (odds ratio, 2.40; 95% confidence interval [CI], 1.07-5.39; P = 0.035). The proportion of patients with AF at last evaluation was higher in ACS (20.0%) than NST (11.9%; P = 0.026). ACS showed a higher risk of incident AF than NST (hazard ratio, 2.95; 95% CI, 1.27-6.86; P = 0.012), which was associated with post-dexamethasone cortisol (hazard ratio, 1.15; 95% CI, 1.07-1.24; P < 0.001), independently of known contributing factors. CONCLUSIONS: Patients with adrenal incidentalomas and ACS are at risk of AF. Electrocardiogram monitoring may be recommended during follow-up.

Diagnostic Accuracy of North America Expert Consensus Statement on Reporting CT Findings in Patients Suspected of Having COVID-19 Infection: An Italian Single-Center Experience.

PURPOSE: To evaluate the diagnostic accuracy of the four standardized categories for CT reporting proposed by the Radiological Society of North America (RSNA) to support a faster triage compared with real-time reverse-transcription polymerase chain reaction (RT-PCR), which is the reference standard for suspected coronavirus disease 2019 (COVID-19), but has long reporting time (6-48 hours). MATERIALS AND METHODS: A retrospective analysis of 569 thin-section CT examinations performed for patients suspected of having COVID-19 from February 27 to March 27, 2020 (peak of infection in Italy) was conducted. The imaging pattern was classified according to the statement by the RSNA as "typical," "indeterminate," "atypical," and "negative" and compared with RT-PCR for 460 patients. Interobserver variability in reporting between a senior and a junior radiologist was evaluated. Use of the vascular enlargement sign in indeterminate cases was also assessed. RESULTS: The diagnosis of COVID-19 was made in 45.9% (211/460) of patients. The "typical" pattern (n = 172) showed a sensitivity of 71.6%, a specificity of 91.6%, and a positive predictive value of 87.8% for COVID-19. The "atypical" (n = 67) and "negative" (n = 123) pattern demonstrated a positive predictive value of 89.6% and 86.2% for non-COVID-19, respectively. The "indeterminate" (n = 98) pattern was nonspecific, but vascular enlargement was most frequently found in patients with COVID-19 (86.1%; P < .001). Interobserver agreement was good for the "typical" and "negative" pattern and fair for "indeterminate" and "atypical" (κ = 0.5; P = .002). CONCLUSION: In an epidemic setting, the application of the four categories proposed by the RSNA provides a standardized diagnostic hypothesis, strongly linked to the RT-PCR results for the "typical," "atypical," and "negative" pattern. In the "indeterminate" pattern, the analysis of the vascular enlargement sign could facilitate the interpretation of imaging features.© RSNA, 2020.

The Steroid Profile of Adrenal Incidentalomas: Subtyping Subjects With High Cardiovascular Risk.

CONTEXT: Steroid profiling by mass spectrometry has shown implications for diagnosis and subtyping of adrenal tumors. OBJECTIVES: To investigate steroid profiles and their cardiovascular correlates in a large cohort of patients with nonsecreting (NS) adrenal incidentalomas and autonomous cortisol secretion (ACS). DESIGN: Cohort study. SETTING: University hospital. PATIENTS: Patients (n = 302) with incidentally discovered adrenal masses, divided into unilateral adenoma and hyperplasia with ACS (n = 46 and n = 52, respectively) and NS (n = 120 and n = 84, respectively). Post-dexamethasone suppression test (DST) cortisol <50 or >50 nmol/L defined NS and ACS, respectively. INTERVENTION: Analysis of 10-steroid panel by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and clinical data (mean follow-up 39 months). MAIN OUTCOME MEASURES: Difference in baseline and post-DST steroid profiles between groups. Correlation with cardiovascular profile. RESULTS: Patients with unilateral adenomas and ACS showed higher cortisol, 11-deoxycortisol, and corticosterone and lower dehydroepiandrosterone than those with NS adenomas. Patients with ACS hyperplasia showed higher cortisol and lower androgens in women than those with NS. Patients with ACS had reduced suppression of post-DST cortisol, 11-deoxycortisol, and corticosterone, irrespective of adrenal morphology. Post-DST cortisol and corticosterone were associated with higher prevalence of severe/resistant hypertension. Patients with ACS unilateral adenomas showed higher incidence of worsening of hypertensive disease and novel cardiovascular events than those with NS, with post-DST cortisol [hazard ratio (HR) 1.02; 95% CI, 1.01 to 1.03; P < 0.001] and baseline corticosterone (HR 1.06; 95% CI, 1.01 to 1.12; P = 0.031) among the main predictors. CONCLUSIONS: Patients with adrenal incidentalomas showed different steroid profiles, depending on functional status and adrenal morphology, with implications for their cardiovascular status.

Larger ascending aorta in primary aldosteronism: a 3-year prospective evaluation of adrenalectomy vs. medical treatment.

OBJECTIVE: Primary aldosteronism is associated with higher cardiovascular morbidity as compared with essential hypertension. Vascular complications encompass myocardial infarction and cerebrovascular events. Aortic damage in primary aldosteronism has never been explored, although a few cases of ascending aorta aneurisms have been reported. DESIGN AND METHODS: We consecutively enrolled patients affected by primary aldosteronism (n = 45) and compared them with patients affected by essential hypertension (n = 47), on an outpatient setting. Echocardiographic data of patients with primary aldosteronism were collected during a mean follow-up of 3 years, in subjects who underwent adrenal surgery (n = 12) and those on mineralocorticoid receptor antagonists (n = 33). RESULTS AND CONCLUSION: We found that patients with primary aldosteronism had larger ascending aorta diameters than those with essential hypertension before starting any specific treatment. Patients with primary aldosteronism did not show significant changes in the size of ascending aorta during a mean of 3 years of follow-up, irrespective of the type of treatment (medical vs. surgical treatment). A longer follow-up will better clarify if worsening of the aortic damage may be better prevented by surgery rather than by mineralocorticoid receptor antagonists.

Pulmonary veno-occlusive disease: the role of CT.

OBJECTIVE: The authors sought to evaluate the diagnostic accuracy of high-resolution computed tomography (HRCT) in the detection of pulmonary veno-occlusive disease (PVOD) in patients with pre-capillary pulmonary arterial hypertension (PAH) of unknown aetiology, and to identify the role of CT in diagnosis and therapy. MATERIALS AND METHODS: The CT scans of 96 patients were retrospectively reviewed and assessed for specific HRCT findings: ground-glass opacities, septal lines and mediastinal lymph nodal enlargement (short diameter ≥1 cm). According to the HRCT findings, patients were divided into PVOD-suspicious and not PVOD-suspicious. Subsequently, a clinical-instrumental evaluation was performed, and the response to therapy and histopathological reports were evaluated. RESULTS: Radiological evaluation based on HRCT findings revealed 29 patients as PVOD-suspicious and 67 as not PVOD-suspicious. The final diagnosis was PVOD in 22 patients and idiopathic PAH in 74 patients. The CT scan showed 95.5 % sensitivity, 89% specificity, 72.5% positive predictive value, and 98.5% negative predictive value, with a diagnostic accuracy of 90.5% in identifying patients with PVOD. CONCLUSIONS: Chest CT can be considered a screening test in the assessment of patients with PAH of unknown aetiology, and the radiologist can help the clinician to identify patients with CT findings that make PVOD highly probable.

Unresectable perihilar cholangiocarcinoma: multimodal palliative treatment.

AIM: To evaluate the survival of patients with unresectable perihilar cholangiocarcinoma (PHC) treated with multimodal palliative approaches. PATIENTS AND METHODS: thirty-two patients were enrolled in a multimodal protocol including: bilateral biliary drainage; Yridium-192 intraluminal brachytherapy (BT); metal biliary stenting; external-beam radiotherapy (EBRT); systemic chemotherapy (ChT). All patients underwent BT and biliary stenting: this was the only treatment for 14 patients, it was combined with EBRT in 11, and with EBRT and ChT in seven. Mean and median survival, complication rates and duration of hospital stay were calculated for each group. RESULTS: BT with EBRT and ChT obtained the best median (15 months) and one year (71.42%) survival followed by BT with EBRT (14 months and 63.63%, respectively). BT with EBRT in a total dose of 54-60 Gy, with or without ChT, led to a significantly higher median survival rate (14 months) than that for BT alone (seven months). CONCLUSION: BT with EBRT, with or without ChT, improves survival and should be considered as a suitable alternative to palliative surgery for patients with unresectable perihilar cholangiocarcinoma.