Econstudentlog

100 Cases in Clinical Medicine

This book is another book in the same series as the 100 Cases in Acute Medicine book. Here’s part of the preface:

“Most doctors think that the most memorable way to learn medicine is to see patients. It is easier to recall information based on a real person than a page in a textbook. Another important element in the retention of information is the depth of learning. Learning that seeks to understand problems is more likely to be accessible later than superficial factual accumulation. This is the basis of problem-based learning, whereby students explore problems with the help of a facilitator. The cases in this book are designed to provide another useful approach, parallel to seeing patients and giving an opportunity for self-directed exploration of clinical problems. They are based on the findings of history taking and examination, together with the need to evaluate initial investigations such as blood investigations, X-rays and electrocardiograms.

These cases are no substitute for clinical experience with real patients, but they provide a safe environment for students to explore clinical problems and their own approach to diagnosis and management. Most are common problems that might present to a general practitioner’s surgery, a medical outpatients clinic or a session on call in hospital. There are a few more unusual cases to illustrate specific points and to emphasize that rare things do present, even if they are uncommon. The cases are written to try to interest students in clinical problems and to enthuse them to find out more. They try to explore thinking about diagnosis and management of real clinical situations.”

As for the ‘interest students in clinical problems and to enthuse them to find out more’-part they certainly succeeded, but I approached this book in a slightly different manner than I did the first one in the series. When I read the acute medicine book, I’d occasionally think to myself while reading the patient history and/or the reported lab results that ‘hey, this sounds a bit like…’ and I’d look up the diagnosis/condition I was considering in order to decide if I wanted to ‘guess’ at that, before moving on to reading the answer part of the case. I did this a few times as well here, but actually most of the pre-answer wiki peeks were related to the interpretation of specific lab results (‘how to interpret some of the arterial blood gas test results’). The reason why I tried to limit myself from looking up stuff before reading the answer was that I wanted to know a little bit about how much of the pathophysiology text (and stuff covered in related texts, such as e.g. Hall’s Handbook and Rogers et al., as well as various medical lectures e.g. from Khan Academy) I could remember. I actually realized when reading the first 100 cases book that there were very few conditions covered there which I had not already read about, or at least seen mentioned, elsewhere; the problem was figuring out which patients had which specific problems. Part of the reason why I often had trouble with that part was incidentally related to the fact that there are some other relevant books I have not read – books such as this one or this one (I’m not planning on reading these, just in case you were wondering). A related point is that doctors have a lot more information available to them than do the people who are sick, and that this is certainly a (small) part of the explanation for why they are better at figuring out what’s wrong than are the people who are sick – symptoms can be non-specific, but if so lab results will often tell you more about where to look and what to look for. I decided beforehand when reading this book that I’d try for fun to keep score and figure out in how many cases I guessed the correct diagnosis; it turned out that I guessed the right diagnosis in roughly one-fifth of the cases and in a few other cases the guess I made was a very plausible differential diagnosis which needed to be ruled out anyway. In a few of them I didn’t get ‘the complete picture’, and I learned something from many of the cases where I knew the (‘diagnosis’-part of the-) right answer. I feel quite certain I would have guessed more of them if I’d spent more time on individual cases; I read the entire book yesterday, and this is not a book you can read in a few hours (I think it took me 12 hours, at least, but I’m not really sure as I didn’t keep track and did take breaks occasionally. Ratios like these – me spending easily 5-10 hours or more on stuff which leads to a post which you’ll read in perhaps 10-15 minutes – are incidentally one reason why I sometimes feel that people reading along here are ‘cheating’ in a way. On the other hand I really can’t complain as long as I’m enabling such ‘cheating’ in the first place…). I got far most of my guesses correct, as in many cases I didn’t guess at all because I wasn’t completely sure what was going on. Of course treatment and management aspects I didn’t ‘guess at’, and that’s an important aspect of the book as well. The conditions I recognized spanned a rather broad range; from colon cancer over HIV seroconversion illness (main differential was malaria – I knew this as well) to COPD, rheumatoid arthritis, bacterial meningitis, obstructive sleep apnea, peripheral neuropathy secondary to undiagnosed type 2 diabetes mellitus, dementia, small cell lung cancer with associated paraneoplastic syndrome, and Parkinson’s disease. As you can probably tell from those diagnoses, like the acute medicine book this book also has some rather depressing cases. Some cases, e.g. a case of cerebral toxoplasmosis secondary to HIV infection (this is actually an AIDS-defining illness, so she had AIDS at the time of admission) and a diet-related vitamin B12 deficiency, were really obvious in retrospect, but in medicine there’s a lot of stuff to remember.

I’ve added some quotes, observations and key points from the book below.

“Cystic fibrosis should always be considered when there is a story of repeated chest infections in a young person. Although it presents most often below the age of 20 years, diagnosis may be delayed until the 20s, 30s, 40s or later in milder cases.”

“Patients with a chronic persistent cough of unexplained cause should have a chest X-ray. When the X-ray is clear the cough is likely to be produced by one of three main causes in non-smokers. Around half of such cases have asthma or will go on to develop asthma over the next few years. Half of the rest have rhinitis or sinusitis with a postnasal drip. In around 20 per cent the cough is related to gastro-oesophageal reflux […] Cough is a common side effect in patients treated with angiotensin-converting enzyme (ACE) inhibitors.”

“This man has signs of chronic liver disease with ascites and oedema. […] The most common cause of chronic liver disease is alcohol. […] However, his alcohol intake is too low to be consistent with the diagnosis of alcoholic liver disease [15-20 units/week, according to the patient history. This was why I initially rejected alcohol-related pathology in this case and (very briefly) considered other causes instead, without coming up with anything (this was another one of those aforementioned obvious ones in retrospect)…]. When the provisional diagnosis is discussed with him, though, he eventually admits that his alcohol intake has been at least 40–50 units per week for the last 20 years. His alcohol intake has increased further during the last year after his marriage had ended.” [Patients sometimes lie to their doctors. This one did. In case you were wondering he died three years later from an esophageal variceal bleed.]

“Patients often become symptomatic due to renal failure only when their glomerular filtration rate (GFR) is less than 15 mL/min [normal range is 90+, US] and thus may present with end-stage renal failure.” [This is an example of a more general point in many medical contexts; our bodies often have a lot of ‘excess capacity’ and redundancies implemented in order to make us less likely to get sick/get symptoms which may decrease our likelihood of survival even if things aren’t optimal. The book actually has other examples illustrating this point, e.g. this: “Patients with central diabetes insipidus typically describe an abrupt onset of polyuria and polydipsia. This is because urinary concentration can be maintained fairly well until the number of AVP-secreting neurones in the hypothalamus decreases to 10–15 per cent of the normal number, after which AVP levels decrease to a range where urine output increases dramatically.”]

“Petechiae are small capillary haemorrhages that characteristically develop in crops in areas of increased venous pressure, such as the dependent parts of the body. Petechiae are the smallest bleeding lesions (pinhead in size), and suggest problems with platelet number or function. Purpura are larger in size than petechiae with variable shape and involve bleeding into subcutaneous tissues. Purpura can be seen in a variety of bleeding disorders […] AML is the most common acute leukaemia in adults with a mean age at presentation of 65 years. Patients with AML generally present with symptoms related to complications of pancytopenia (eg, anemia, neutropenia, and thrombocytopenia), including weakness, breathlessness and easy fatigability, infections of variable severity, and/or haemorrhagic findings such as gingival bleeding, ecchymoses, epistaxis, or menorrhagia.”

“Vegans who omit all animal products from their diet often have subclinical vitamin B12 deficiency […] Vitamin B12 deficiency may occur in strict vegetarians who eat no dairy products. […] Typical neurological signs are position and vibration sense impairment in the legs, absent reflexes and extensor plantars.”

“Malaria prophylaxis is often not taken regularly. Even when it is, it does not provide complete protection against malaria […] A traveller returning from a malaria endemic region who develops a fever has malaria until proven otherwise.”

“Peripheral oedema may occur due to local obstruction of lymphatic or venous outflow or because of cardiac, renal, pulmonary or liver disease. Unilateral oedema is most likely to be due to a local problem […] Bilateral oedema may be due to cardiac, liver or renal disease. […] Pitting oedema needs to be distinguished from lymphoedema, which is characteristically non-pitting. This is tested by firm pressure with the thumb for approximately 10 s. If the oedema is pitting, an indentation will be present after pressure is removed. […] frothy urine is a clue to the diagnosis of nephrotic syndrome and is commonly noted by patients with heavy proteinuria.”

“80% of C. difficile infections occur in people aged over 65 years since a lower density and fewer species of gut bacteria make them more susceptible to colonisation by C. difficile […] 20% of hospital patients and those in long-term care facilities are colonised with C. difficile. […] C. difficile infection should be suspected in any hospital patient who develops diarrhoea.”

“ADPKD [Autosomal Dominant Polycystic Kidney Disease] is the most common inherited renal disease, occurring in approximately 1:600 to 1:1000 individuals. Although the name ‘ADPKD’ is derived from renal manifestations of cyst growth leading to enlarged kidneys and renal failure, this is a systemic disorder manifested by the presence of hepatic cysts, diverticular disease, inguinal hernias, mitral valve prolapse, intracranial aneurysms and hypertension. […] Patients with ADPKD are often asymptomatic. […] Flank pain is the most common symptom […] Hypertension occurs early in the course of this disease, affecting 60% of patients with normal renal function. Approximately 50% of ADPKD patients will develop end-stage renal failure.”

“Transient small nodes in the neck or groin are common benign findings. However, a 3 × 4 cm mass of nodes for 2 months is undoubtedly abnormal. […] Lymph nodes are normally barely palpable, if at all. The character of enlarged lymph nodes is very important. In acute infections the nodes are tender, and the overlying skin may be red. Carcinomatous nodes are usually very hard, fixed and irregular. The nodes of chronic leukaemias and lymphomas are non-tender, firm and rubbery.  […] The typical systemic symptoms of lymphoma are malaise, fever, night sweats, pruritus, weight loss, anorexia and fatigue.”

“Colonic diverticula are small outpouchings that are most commonly found in the left colon. […] Inflammation in a diverticulum is termed diverticulitis. […] Diverticular disease is a common finding in the elderly Western population and may be asymptomatic or cause irritable bowel syndrome-type symptoms. […] Diverticular disease is a common condition; its presence can distract the unwary doctor from pursuing a coincident condition.”

“Tension type headaches are the commonest headaches in the general population. The typical presentation is of mild to moderate headache, nonthrobbing, bilateral with no associated symptoms. Cluster headaches are characterised by attacks of severe unilateral orbital or temporal pain, accompanied by autonomic features such as nasal congestion, lacrimation and rhinorrhoea. Migraines are often preceded by characteristic symptoms such as flashing lights and are often unilateral. Nausea and photophobia may occur during an attack. Brain tumours cause headaches by causing raised intracranial pressure. The headache is worse after coughing and is often associated with nausea and vomiting. […] The sudden onset of a headache within seconds or a few minutes is characteristic of a subarachnoid haemaorrhage (SAH). […] Patients with SAH often describe the pain as ‘the worst headache in my life’. [And in many cases it’s also the last headache they ever will have:] SAH is associated with a mortality rate of up to 50%.”

“He drinks 35 units of alcohol per week and smokes 30 cigarettes per day.” [Aargh! Another one of those! But at least this one didn’t lie about his drinking habits. … But it gets worse:] “No history was available from the patient [she’s in a coma], but her partner volunteered the information that they are both intravenous heroin addicts. She is unemployed, smokes 25 cigarettes per day, drinks 40 units of alcohol per week and has used heroin for the past 4 years.” [Dammit! Some of these histories are depressing in more than one way. The woman had been found unconscious by her partner. My first thought when reading the case story about the woman and the lab results was that, ‘This reminds me of that movie I saw a while back, what’s it called..?’ – I can’t remember the name of the movie, but it’s not important. I want to quote a bit more extensively from the answer part of this case because I thought it was sort of fascinating in a way; it illustrates how a drug overdose isn’t always just a problem because of the drug overdose:]

“This patient has acute renal failure as a result of rhabdomyolysis. Severe muscle damage causes a massively elevated serum creatine kinase (CK) level and a rise in serum potassium and phosphate levels. In this case, she has lain unconscious on her left arm for many hours due to an overdose of alcohol and intravenous heroin. As a result, she has developed severe ischaemic muscle damage, causing release of myoglobin, which is toxic to the kidneys. […] Acute renal failure due to rhabdomyolysis causes profound hypocalcaemia in the oliguric phase due to calcium sequestration in muscle and reduced 1,25-dihydroxycalciferol levels, often with rebound hypercalcaemia in the recovery phase. This woman’s consciousness level is still depressed as a result of opiate and alcohol toxicity, and she has clinical and radiological evidence of aspiration pneumonia. She has mixed metabolic and respiratory acidosis (low pH, bicarbonate) due to acute renal failure and respiratory depression (pCO2 elevated). Her arterial oxygenation is reduced due to hypoventilation and pneumonia. She also has compartment syndrome in her arm due to massive swelling of her damaged muscles. This patient has life-threatening hyperkalaemia with electrocardiogram (ECG) changes. […] Emergency treatment involves intravenous calcium gluconate, which stabilizes cardiac conduction, and intravenous insulin/glucose, intravenous sodium bicarbonate and nebulized salbutamol, all of which temporarily lower the plasma potassium by increasing the cellular uptake of potassium. However, these steps should be regarded as holding measures while urgent dialysis is being organized. The chest X-ray and clinical findings indicate consolidation of the left lower lobe. This patient should initially be managed on an intensive care unit. She will require antibiotics for her pneumonia and will require a naloxone infusion or mechanical ventilation for her respiratory failure. The patient should have vigorous rehydration with monitoring of her central venous pressure. If a good urinary flow can be maintained, urinary pH should be kept greater than 7.0 by bicarbonate infusion, which prevents the renal toxicity of myoglobin. This patient also needs to be considered urgently for surgical fasciotomy to relieve the compartment syndrome in her arm.”

Back when I read the Acute Muscle Injuries text, compartment syndrome was sort of a worst-case-scenario. Here it’s just one of multiple problems, each of which on their own would be quite terrible. I should incidentally note in case you were wondering if all of the patients in this book are alcoholics that most of them are not – but that they mention in the coverage that: “In some surveys alcohol is linked directly to around 25% of acute medical admissions.” I looked around very briefly for those numbers because they sounded very high to me, but I didn’t find much. This paper had an estimate of 6%, but that’s out of all hospital admissions and you’d expect the proportion of all admissions involving alcohol to be significantly lower than the proportion of acute admissions. Note in that context that ‘the true number’ in the former case is to some extent unknowable – though you can try to estimate it, as people do – as e.g. alcohol’s role in certain cancers is quite difficult to figure out in general, and impossible to figure out at the individual level; it makes sense to say that drinking alcohol increases your risk of breast cancer (and perhaps that’s not even the best example as we’re quite sure alcohol has a role there, a level of certainty we in other areas of oncology do not have), but deciding with certainty whether patient X’s specific case of breast cancer was alcohol-related or not is impossible – ‘it may have been a contributing factor’ is probably the closest you can get, we don’t have a test for that. Same goes for a cardiovascular event – ‘alcohol may have played a role’, but that’s it. Perhaps also worth remembering here is incidentally that on a related note some epidemiological findings trying to have a closer look at precisely these sorts of things may have results which are partially explained by statistical artifacts unrelated to the ‘true’ associated risk; a smoker who drinks a lot is highly likely to die from various alcohol- and smoking-related causes at a relatively early age. Such early deaths may well make people with such habits less likely to get old enough to get prostate cancer (the risk of which increases dramatically with age), even if alcohol and smoking on their own perhaps actually increase the risk of prostate cancer, in the sense that the effects of both alcohol and smoking may be to make those cells more likely to turn malignant (I don’t know if this is actually the case or not, it’s just the sort of thing you need to watch out for). There are ways around such problems – a competing risks framework is important to have in mind here – but problems of this sort are sometimes hard to avoid and/or deal with.

They don’t talk about these things in the book, but they talk about a lot of other interesting stuff, and I can’t cover all of it. One thing I have yet to cover which I thought I should include as a small favour to a friend reading along is this part, from the very last pages of the book:

“Traditional Chinese medicine includes herbal therapy, acupuncture, massage and dietary therapy. There is potential for developing novel treatments for diseases such as asthma and food allergies with Chinese herbs. However, there is concern over the lack of standardization and controlled clinical trials. Chinese herbal medicines containing aristolochic acid have been implicated in a specific nephropathy characterised by extensive interstitial fibrosis with atrophy and loss of the tubules, with thickening of the walls of the interlobular and afferent arterioles. Blood pressure is generally normal or only modestly elevated. Patients presenting with a creatinine < 200 will generally stabilise their renal function after stopping the Chinese medications, but patients with worse kidney function will generally progress to end-stage kidney failure.”

I liked the book and I gave it three stars on goodreads. You need to be fluent in ‘medical textbook’ in order to get much out of this book, but if you have some medical knowledge I believe you’ll be quite likely to find the books in this series quite interesting.

June 8, 2014 - Posted by | alcohol, books, medicine

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