Generalizability of Deep Neural Networks for Vertical Cup-to-Disc Ratio Estimation in Ultra-Widefield and Smartphone-Based Fundus Images

Purpose

To develop and validate a deep learning system (DLS) for estimation of vertical cup-to-disc ratio (vCDR) in ultra-widefield (UWF) and smartphone-based fundus images.

Methods

A DLS consisting of two sequential convolutional neural networks (CNNs) to delineate optic disc (OD) and optic cup (OC) boundaries was developed using 800 standard fundus images from the public REFUGE data set. The CNNs were tested on 400 test images from the REFUGE data set and 296 UWF and 300 smartphone-based images from a teleophthalmology clinic. vCDRs derived from the delineated OD/OC boundaries were compared with optometrists' annotations using mean absolute error (MAE). Subgroup analysis was conducted to study the impact of peripapillary atrophy (PPA), and correlation study was performed to investigate potential correlations between sectoral CDR (sCDR) and retinal nerve fiber layer (RNFL) thickness.

Results

The system achieved MAEs of 0.040 (95% CI, 0.037-0.043) in the REFUGE test images, 0.068 (95% CI, 0.061-0.075) in the UWF images, and 0.084 (95% CI, 0.075-0.092) in the smartphone-based images. There was no statistical significance in differences between PPA and non-PPA images. Weak correlation (r = -0.4046, P < 0.05) between sCDR and RNFL thickness was found only in the superior sector.

Conclusions

We developed a deep learning system that estimates vCDR from standard, UWF, and smartphone-based images. We also described anatomic peripapillary adversarial lesion and its potential impact on OD/OC delineation.

Translational Relevance

Artificial intelligence can estimate vCDR from different types of fundus images and may be used as a general and interpretable screening tool to improve community reach for diagnosis and management of glaucoma.

Can propensity score matching replace randomized controlled trials?

Randomized controlled trials (RCTs) have long been recognized as the gold standard for establishing causal relationships in clinical research. Despite that, various limitations of RCTs prevent its widespread implementation, ranging from the ethicality of withholding potentially-lifesaving treatment from a group to relatively poor external validity due to stringent inclusion criteria, amongst others. However, with the introduction of propensity score matching (PSM) as a retrospective statistical tool, new frontiers in establishing causation in clinical research were opened up. PSM predicts treatment effects using observational data from existing sources such as registries or electronic health records, to create a matched sample of participants who received or did not receive the intervention based on their propensity scores, which takes into account characteristics such as age, gender and comorbidities. Given its retrospective nature and its use of observational data from existing sources, PSM circumvents the aforementioned ethical issues faced by RCTs. Majority of RCTs exclude elderly, pregnant women and young children; thus, evidence of therapy efficacy is rarely proven by robust clinical research for this population. On the other hand, by matching study patient characteristics to that of the population of interest, including the elderly, pregnant women and young children, PSM allows for generalization of results to the wider population and hence greatly increases the external validity. Instead of replacing RCTs with PSM, the synergistic integration of PSM into RCTs stands to provide better research outcomes with both methods complementing each other. For example, in an RCT investigating the impact of mannitol on outcomes among participants of the Intensive Blood Pressure Reduction in Acute Cerebral Hemorrhage Trial, the baseline characteristics of comorbidities and current medications between treatment and control arms were significantly different despite the randomization protocol. Therefore, PSM was incorporated in its analysis to create samples from the treatment and control arms that were matched in terms of these baseline characteristics, thus providing a fairer comparison for the impact of mannitol. This literature review reports the applications, advantages, and considerations of using PSM with RCTs, illustrating its utility in refining randomization, improving external validity, and accounting for non-compliance to protocol. Future research should consider integrating the use of PSM in RCTs to better generalize outcomes to target populations for clinical practice and thereby benefit a wider range of patients, while maintaining the robustness of randomization offered by RCTs.

Prehabilitation programs in liver resection: a narrative review

BACKGROUND AND OBJECTIVE

Liver resection (LR) is a commonly performed surgical procedure for the management of hepatocellular carcinoma and other liver conditions. Despite its benefits in providing patients a potential cure, it is also associated with significant postoperative complications and prolonged recovery periods. In recent years, pre-operative rehabilitation (prehabilitation) has emerged as an up-and-coming strategy to optimize patients' physical, psychological and functional status before LR, leading to improved surgical and patient postoperative outcomes. Hence, our review aims to explore and synthesize the existing literature on prehabilitation in LR to provide an overview of the current evidence to help guide physicians in managing their patients.

METHODS

A comprehensive literature search was conducted in multiple electronic databases from inception to July 2023. The search strategy was tailored to capture studies investigating the role of prehabilitation in LR, and the factors that contribute to beneficial outcomes in the postoperative period.

KEY CONTENT AND FINDINGS

Prehabilitation programs encompass a multifaceted approach to enhance surgical outcomes and patient well-being. This considers the specific needs of the varying patient populations, such as the elderly, or the cancer ridden. Improving physical fitness, nutritional supplementation and psychological support are the common tenets of prehabilitation. In physical prehabilitation, patients are engaged in intensive physical exercise often by means of a cycle ergometer. Addressing nutritional deficiencies through supplements and dietary interventions is also vital. Psychosocial assessments, advance care planning, music therapy, and progressive relaxation exercises are shown to enhance patient resilience and well-being. In addition, innovative approaches such as optimizing fluid balance, avoiding epidural analgesia, perioperative steroid administration, phosphate correction and branched-chain amino acid supplementation are being explored.

CONCLUSIONS

Prehabilitation is important in optimizing patients before LR and is key in improving postoperative outcomes. Several prehabilitation strategies exist, but no formal consensus exists on patient selection and an ideal program.

Mirizzi Syndrome-The Past, Present, and Future

Mirizzi syndrome is a complication of gallstone disease caused by an impacted gallstone in the infundibulum of the gallbladder or within the cystic duct, causing chronic inflammation and extrinsic compression of the common hepatic duct or common bile duct. Eventually, mucosal ulceration occurs and progresses to cholecystobiliary fistulation. Numerous systems exist to classify Mirizzi syndrome, with the Csendes classification widely adopted. It describes five types of Mirizzi syndrome according to the presence of a cholecystobiliary fistula and its corresponding severity, and whether a cholecystoenteric fistula is present. The clinical presentation of Mirizzi syndrome is non-specific, and patients typically have a longstanding history of gallstones. It commonly presents with obstructive jaundice, and can mimic gallbladder, biliary, or pancreatic malignancy. Achieving a preoperative diagnosis guides surgical planning and improves treatment outcomes. However, a significant proportion of cases of Mirizzi syndrome are diagnosed intraoperatively, and the presence of dense adhesions and distorted anatomy at Calot's triangle increases the risk of bile duct injury. Cholecystectomy remains the mainstay of treatment for Mirizzi syndrome, and laparoscopic cholecystectomy is increasingly becoming a viable option, especially for less severe stages of cholecystobiliary fistula. Subtotal cholecystectomy is feasible if total cholecystectomy cannot be performed safely. Additional procedures may be required, such as common bile duct exploration, choledochoplasty, and bilioenteric anastomosis. Conclusions: There is currently no consensus for the management of Mirizzi syndrome, as the management options depend on the extent of surgical pathology and availability of surgical expertise. Multidisciplinary collaboration is important to achieve diagnostic accuracy and guide treatment planning to ensure good clinical outcomes.

Painless nodules on legs

The location of the nodules and the patient's history were important diagnostic clues. The punch biopsy confirmed our suspicions.

Opisthorchis viverrini-Current Understanding of the Neglected Hepatobiliary Parasite

Opisthorchiasis due to Opisthorchis viverrini infection continues to be a significant public healthcare concern in various subregions of Southeast Asia, particularly in Thailand, Laos, Cambodia, Myanmar, and Vietnam. The main mode of transmission is via consumption of raw or undercooked fish, which is deeply embedded in the culture and tradition of the people living near the Mekong River. After ingestion, the flukes migrate to the bile ducts, potentially causing many hepatobiliary complications, including cholangitis, cholecystitis, cholelithiasis, advanced periductal fibrosis and cholangiocarcinoma. Several mechanisms of opisthorchiasis-associated cholangiocarcinogenesis have been proposed and elucidated in the past decade, providing insight and potential drug targets to prevent the development of the sinister complication. The gold standard for diagnosing opisthorchiasis is still via stool microscopy, but the advent of novel serological, antigen, and molecular tests shows promise as more convenient, alternative diagnostic methods. The mainstay of treatment of opisthorchiasis is praziquantel, while treatment of opisthorchiasis-associated cholangiocarcinoma depends on its anatomic subtype and resectability. Thus far, the most successful fluke control programme is the Lawa model based in Thailand, which raised awareness, incorporated education, and frequent surveillance of intermediate hosts to reduce transmission of opisthorchiasis. Development of vaccines using tetraspanins shows promise and is currently ongoing.