How to apply clinical cases and medical literature in the framework of a modified “failure mode and effects analysis” as a clinical reasoning tool – an illustration using the human biliary system

Clinicians, medical educators, and medical students use various clinical reasoning tools such as Ishikawa diagram (which is also known as “cause-and-effect diagram”) to enhance their clinical experience and reasoning skills. The methodology of applying an Ishikawa diagram in a clinical setting is illustrated in another article [1]. The methods that can be applied to gather information for an Ishikawa diagram include brain storming, focus group discussion, interview, survey, and literature searches and review are discussed in a book chapter [2]. This article illustrates how to modify and apply failure mode and effects analysis (FMEA) to provide inputs into an Ishikawa diagram which in turn can be used as a clinical reasoning tool.

FMEA is a tool developed by engineers to systematically assess a complex design or process in order to identify elements that have a risk of failure [3]. In the late 1940s, FMEA was established and deployed by reliability engineers to identify potential failures in military systems [4]. Simplistically, the FMEA approach includes a meticulous study on the mode or mechanism by which a failure may occur and the effect(s) that it may cause. The severity of the effect (S), the probability of a failure occurring (O), and the probability that the failure would not be detected (D), are computed or estimated. Then, a risk priority number (RPN) is calculated by multiplying S, O, and D. The RPN is then used to prioritize the remedial and/or preventive measures. The FMEA approach is an ongoing iterative process. It should be updated when there is a change in the process or design, or when there is a failure or when a near-miss failure occurs. The ultimate objective of an FMEA is to provide a platform for the prevention, or at least reduce the likelihood and improve the detection, of failure in a system.

How can I relate this engineering approach to an application in medicine? In this article, failure is defined as an abnormality caused by infective, inflammatory, obstructive, malignancy, autoimmune and other pathological processes. I may not be able to relate the FMEA approach to the entirety of a complex human being with multidimensional complexities including psychosocial components, when an individual presents with a clinical manifestation (that is, a “failure”). Nonetheless, I am illustrating an application of the FMEA approach to a specific subsystem in a human. The “design or anatomy” of a human body and its underlying physiological processes have a potential risk of failing at its various parts anatomically and physiologically. The effect(s) of the failure could be manifested as clinical features (symptoms and signs). The severity, occurrence, and detection of the failure are complex and difficult to be estimated to compute a RPN. Hence, I am excluding RPN in this FMEA approach which I call a “modified FMEA” (in short, mFMEA). The ultimate objective of mFMEA is to provide a methodology to clinicians, medical educators, and medical students, to integrate in their clinical reasoning process and to deploy relevant clinical cases to set the scenario for teaching and learning a specific topic.

The mFMEA approach is applicable for general practitioners (GPs)/family physicians, specialists in various fields (internal medicine, surgery, emergency, intensive care, and so on), medical educators, and medical students. The bottom line is that a patient will always present with symptoms and signs (clinical features or syndromes) that need to be analyzed and put in perspective in an individualized context. An experienced clinician such as a physician or specialist may reach a spot diagnosis or provisional diagnosis, and manage the patient accordingly in a reasonably efficient timeframe. In an experienced diagnostician, the clinical reasoning and diagnostic skill seem to have become second nature to him/her, and the skills may not be explicit to an observer. However, a junior clinician or medical student may start from the first principle to work out a list of differential diagnoses using various clinical reasoning tools such as brain storming, mind mapping, and the Ishikawa diagram/fishbone diagram or cause-and-effect diagram [1]. For example, if a patient presents with a main complaint of pain in the right upper quadrant (RUQ) of the abdomen, a clinician will have a list of differential diagnoses including cholecystitis, cholelithiasis, hepatitis, peptic ulcer, pancreatitis, and referred pain. These can be illustrated in an Ishikawa diagram (Fig. 1) which is subject to ongoing update. The Ishikawa diagram comprises “gastroenterology”, “other systems”, and “miscellaneous”. The biliary system is a branch under “gastroenterology”. The Ishikawa diagram will be continually expanded and refined based on other associated symptoms in the individualized context of the patient. Then, one may ask how a mFMEA approach would fit in a clinical setting. A mFMEA can provide inputs into an Ishikawa diagram. Once you have listed the common causes in an Ishikawa diagram via brainstorming, discussion, or self-directed learning process, you turn to mFMEA to explore the potential causes of the human biliary system (Fig. 1). I would like to elaborate this in the following paragraphs.

An English scientist, Richard Dawkins, once said, “Biology is the study of complicated things that have the appearance of having been designed with a purpose.” The notable quote underpins many biological and physiological processes within a human body; for example, the human biliary system. When we review the anatomical and physiological processes of the biliary system, we should ask “what is the potential failure and its effect(s)”, “the associated main clinical features”, and “investigations that can help a clinician to diagnose” at each anatomical part and physiological process, and document them in a mFMEA table (Table 1). The mFMEA table comprises six columns: “Anatomy and physiology”, “Potential failure or pathophysiological process”, “Effects of the failure”, “Main clinical features (symptoms and signs)”, “Investigation”, and “Note”. We can start with common knowledge found in the medical literature, and then proceed to search and extract the relevant medical and surgical cases (generally known as clinical cases in this article) to fill the mFMEA table. Establishing a mFMEA can be a teamwork project or a self-directed learning process, or a mix of teamwork followed by self-directed learning to continually update it.

For example, the human biliary system is used for illustration (Table 1). Firstly, review the major anatomy and physiology of the biliary system, and list them in the first column. The anatomical figure of the biliary system (Fig. 2) will be helpful to provide visual cues to the physiological process. At each anatomical part or physiological process, we should explore what can be the potential failure or pathophysiological process, the corresponding effect(s), the resulting clinical features (symptoms and signs), investigation that can help a clinician to diagnose (in addition to the patient’s clinical history and physical examination), and special note. The treatment is not included in the table because the treatment option is dependent on the context of each individual. The note column is used for highlighting a key message or reminder, for example the authors of the case of clonorchiasis encourage clinicians to consider clonorchiasis or opisthorchiasis infection a possible diagnosis for all undiagnosed abdominal pain because the infection has the propensity to cause hepatic fibrosis, liver cancer and cholangiocarcinoma [5]. Also, the “note” column can be used to record citation of relevant new or additional cases (see Table 1).

Let us walk through the steps to establish a mFMEA in Table 1. You may refer to Table 1 and the references for citations of the relevant cases. Starting from the gallbladder, we have already known its common “potential failures” such as cholecystitis, cholecystolithiasis, and gallbladder cancer. By searching the medical literature, I have found some other failures such as gallbladder perforation, herniation, and torsion. The associated effects of the failures include obstruction, necrosis, and hernia. The main clinical features range from asymptomatic to abdominal pain with or without jaundice. The relevant investigations include abdominal ultrasound, computed tomography (CT) scan, endoscopic retrograde cholangiopancreatography (ERCP), and magnetic resonance cholangiopancreatography (MRCP).

In the cystic duct and common bile duct, obstruction (caused by gallstone or cancer) and infection are two common potential failures. In the hepatic duct (intrahepatic and extrahepatic duct), the potential failures include obstruction, infection, abscess, cancer, congenital-related abnormality, for example Caroli’s disease (congenital dilatation of the intrahepatic bile ducts), choledochal cyst, and biliary atresia, immune-mediated destruction of the intrahepatic bile ducts (primary biliary cirrhosis), intense inflammatory fibrosis of the intrahepatic and extrahepatic bile ducts (primary sclerosing cholangitis), immunoglobulin G4 (IgG4)-related cholangitis, and abnormality in the genes encoding for the bile canaliculi formation (progressive familial intrahepatic cholestasis). In addition to abdominal pain with or without jaundice, other symptoms and signs include systemic features such as fever, nausea, vomiting, anorexia, weight loss, anemia, fatigue, pruritus, steatorrhea, dark urine, and hepatosplenomegaly. Other investigations include liver function test, liver biopsy, antimitochondrial antibody, and serum IgG4 level according to the context of the patient.

In the process of bile synthesis, conjugation, and transport, the potential failures are broadly categorized into Gilbert syndrome, Crigler–Najjar syndrome, Dubin–Johnson syndrome, and Rotor syndrome. The clinical features range from asymptomatic to abdominal pain with or without jaundice. The investigations include special genetic tests, liver biopsy, and urinary coproporphyrin level, and plasma sulfobromophthalein depending on the clinical history of the patient.

Other anatomical parts that relate to the biliary system include portal vein, hepatic artery, hepatic vein, sphincter of Oddi, ampulla of Vater, and the pancreas. The potential failures include iatrogenic injury from surgical procedure, thrombosis, spasm, stenosis, and cancer. The clinical features include Courvoisier sign, legs edema, ascites, fatigue, anorexia, weight loss, abdominal pain, and jaundice. Special investigations include Doppler ultrasound of the suprahepatic and cava veins, abdominal CT and angiography, and sphincter of Oddi manometry.

The relevant potential failures of the hematological process, which is not restricted to a particular anatomical structure, include glucose-6-phosphate dehydrogenase (G6PD) deficiency, paroxysmal nocturnal hemoglobinuria (PNH), and hereditary spherocytosis. These abnormalities result in excessive hemolysis of red blood cells leading to hyperbilirubinemia. The clinical features include anemia, jaundice, splenomegaly, and kernicterus (in serious cases). The special investigations include serum G6PD level, genetic test, peripheral blood smear, and spherocyte osmotic fragility test.

An example of endocrinological condition has been reported in the New England Journal of Medicine - A patient with poorly controlled diabetes mellitus has excessive glucose in the blood leading to an increase in glycogen storage in the liver and inhibition of glycogenolysis resulting in glycogenic hepatopathy. The condition is manifested as hepatomegaly and pain in the RUQ of the abdomen.

After establishing the mFMEA in Table 1, I can update the relevant Ishikawa diagram for “pain in the RUQ of the abdomen” (Fig. 1) to include the detailed inputs for the “biliary pathology” as shown in Fig. 3.

There are many sources of clinical cases such as:

How to keep a mFMEA table up to date.

Advantages of weaving clinical cases into a mFMEA.

The mFMEA can be deployed as a tool to generate inputs for an Ishikawa diagram. Clinicians may apply the tool in their clinical reasoning process; while medical educators may select relevant clinical cases to set the scenarios to teach and facilitate a discussion among medical students, and relate the clinical cases back into a relevant mFMEA and Ishikawa diagram.