The Great Imitator

Many diseases are difficult to diagnose, because they don't follow a specific pattern or they imitate the pattern of another disease.

This happens when the signs and symptoms of the disease are non-sensitive and non-specific.
Multi-system diseases usually have very variable presentations.

• Neoplasms
• Diffuse large B-cell lymphoma
• Infectious diseases
• Brucellosis
• Lyme disease
• Malaria
• Nocardiosis
• Syphilis
• Tuberculosis
• Autoimmune diseases
• Coeliac disease
• Fibromyalgia
• Multiple sclerosis
• Psoriatic arthritis
• Systemic lupus erythematosus
• Metabolic and endocrine diseases
• Addison disease
• Amyloidosis
• Hypoglycaemia (great imitator of a stroke)
• Phaeochromocytoma
• Pulmonary embolism
• Sarcoidosis
• Sleep apnoea

Surgical sieve

When considering any clinical pattern it is important to consider what aetiology (cause) would fit. A systemic approach allows you to produce a list of possible diagnoses. This is a differential diagnosis. The "top differential" is the most likely diagnosis at that moment in time.

It is also important to promptly test for conditions which would have severe consequences in the short term if missed. These should be excluded from the differential, with sufficient evidence, as soon as possible. E.g. abdominal pain in a young woman could be an ectopic pregnancy. A prompt pregnancy test with a negative result will show that pregnancy is unlikely.

The surgical sieve refers to a system of structured thought when building a differential diagnosis. There are many mnemonics which can be helpful to remember these different categories.

#1 VITAMIN CDEF

• V: vascular
• I: infective / inflammatory
• T: traumatic
• A: autoimmune
• M: metabolic
• I: iatrogenic
• Easily forgotten but very common.
• N: neoplastic / neurological / nutritional
• C:  congenital diseases
• Present since birth
• D: degenerative
• E: environmental
• F: functional

F can be substituted for U, meaning 'unknown cause'. This is more all-encompassing than 'functional' because it clearly contains idiopathic diseases.

 

#2 MEDIC HAT PINE

M: metabolic
E: endocrinological
D: degenerative
I: inflammatory / infective
C: congenital diseases

H: haematological
A: autoimmune
T: traumatic

P: psychiatric / neurological
I: idiopathic / iatrogenic
N: neoplastic
E: environmental

Fever of unknown origin

Disease class: Fever

Also known as

• FUO
• Pyrexia of unknown origin

Fever

Also known as

• Pyrexia
• Febrile response

 

Subtypes

• Fever of unknown origin

Wells' Criteria

Calculates Wells' Score for risk of DVT.

The Wells’ DVT Criteria can be used in the outpatient and emergency department setting. By risk stratifying to low risk (Wells’ Score <2) and a negative d-dimer the clinician can exclude the need for ultrasound (US) to rule out DVT.  

Patients can be divided into “DVT unlikely” and “DVT likely” groups based on Wells score.
An additional moderate risk group can be added based on the sensitivity of the d-dimer being used.

CHA2DS2-VASc

Also known as

• CHADS-VASc

Calculates stroke risk for patients with atrial fibrillation, possibly better than the CHADS₂ Score.

CHA2DS2-VASc Score	Stroke Risk %	95% CI
0	0	-
1	1.3	-
2	2.2	-
3	3.2	-
4	4.0	-
5	6.7	-
6	9.8	-
7	9.6	-
8	12.5	-
9	15.2	-

C 
 Congestive heart failure (or Left ventricular systolic dysfunction)
1 H
 Hypertension: blood pressure consistently above 140/90 mmHg (or treated hypertension on medication)
1 A₂
 Age ≥75 years
2 D
 Diabetes Mellitus
1 S₂
 Prior Stroke or TIA or thromboembolism
2 V
 Vascular disease (e.g. peripheral artery disease, myocardial infarction, aortic plaque)
1 A
 Age 65–74 years
1 Sc
 Sex category (i.e. female sex)
1

CURB-65

Estimates mortality of community-acquired pneumonia to help determine inpatient vs. outpatient treatment.

Parameters

• C : Confusion (new onset).
• U : Urea. BUN > 19 mg/dL (> 7 mmol/L).
• R : Respiratory rate ≥ 30 breaths per minute
• B : Blood pressure. Systolic BP < 90 mmHg or Diastolic BP ≤ 60 mmHg.
• 65 : Aged 65 or older.

 

Prognosis

2: Moderate risk group: 6.8% 30-day mortality. Consider inpatient treatment or outpatient with close followup.
5: Highest risk group: 27.8% 30-day mortality. Consider inpatient treatment with possible intensive care admission.

HAS-BLED

Estimates risk of major bleeding for patients on anticoagulation to assess quality of atrial fibrillation care.

H	Hypertension: (uncontrolled, >160 mmHg systolic)	1
A	Abnormal renal function: Dialysis, transplant, Cr >2.26 mg/dL or >200 µmol/L Abnormal liver function: Cirrhosis or Bilirubin >2x Normal or AST/ALT/AP >3x Normal	1 1
S	Stroke: Prior history of stroke	1
B	Bleeding: Prior Major Bleeding or Predisposition to Bleeding	1
L	Labile INR: (Unstable/high INR), Time in Therapeutic Range < 60%	1
E	Elderly: Age > 65 years	1
D	Prior Alcohol or Drug Usage History (≥ 8 drinks/week) Medication Usage Predisposing to Bleeding: (Antiplatelet agents, NSAIDs)	1 1

Hyperventilation

Disease class: Respiration disorders

Apgar score

A method to quickly assess the health of newborn children and predict risk of infant mortality.

 

History

Invented in 1952 by Dr Virginia Apgar.

SOFA

Sequential organ failure assessment score

 

See also

• APACHE score

SAPS

Simplified Acute Physiology Score

 

See also

• APACHE score

APACHE

Acute Physiology, Age, Chronic Health Evaluation 

Current version: IV

  

Parameters (APACHE II)

1. AaDO2 or PaO2 (depending on FiO2)
2. Temperature (rectal)
3. Mean arterial pressure
4. pH arterial
5. Heart rate
6. Respiratory rate
7. Sodium (serum)
8. Potassium (serum)
9. Creatinine
10. Haematocrit
11. White blood cell count
12. Glasgow Coma Scale

 

Prognosis (APACHE II)

 <15

Mortality: 0.29 %
Admitted to ICU: 6.53 %

15-20

Mortality:  11.33 %
Admitted to ICU: 28.00 %

21-25

Mortality: 19.80 %
Admitted to ICU: 46.53 %

>25

Mortality: 60.61 %
Admitted to ICU: 81.82 %

 

History

• 1981: APACHE published
• 1985: APACHE II published (score 0-71)
• 1991: APACHE III published (score 0-299)
• 2006: APACHE IV published (score 0-286)

 

See also

• NEWS (National Early Warning Score)
• MEWS (Modified Early Warning Score)
• SAPS (Simplified Acute Physiology Score)
• SOFA (Sequential organ failure assessment score)

Tourettism

Tourettism refers to a presentation of a patient with signs and symptoms which resemble Tourette syndrome, in the absence of the syndrome itself.

Similar signs

• Chorea
• Myoclonus
• Dystonia
• Torsion dystonia
• Idiopathic dystonia

 

Differential diagnosis

• Down syndrome
• Hepatolenticular degeneration
• Huntington's disease 
• Intellectual disability
• Schizophrenia
• Stereotypic movement disorder

Infectious or post-infectious 

• Encephalitis
• Sydenham's chorea

Drug-induced

• Levodopa
• Carbamazepine
• Lamotrigine
• Phenytoin
• Phenobarbital
• Haloperidol

Full blood count

This is a profile of blood tests. 

 

Includes:

• RBC count
• White blood cell count 
• Platelet count
• Haemaglobin
• MCV
• MCHC
• HCT

 

Indications

• Anaemia

Laboratory services

Specimen Type: Blood
Sample type: EDTA

 

Turnaround time

Urgent: 1 hour 
Routine: 4 hours

 

Reference Interval:

Test	Male	Female	Units
Haemoglobin (Hb)	130 - 180	115 - 165	g/L
White Blood Cell (WBC)	4 - 11	4 - 11	109/L
Platelets (Plt)	150 - 450	150 - 450	109/L
Red Blood Cell (RBC)	4.3 - 5.8	3.9 - 5.4	1012/L
Mean Cell Volume (MCV)	79 - 101	79 - 101	fL
Haematocrit (Hct or PCV)	0.39 - 0.5	0.36 - 0.47	L/L
Mean Cell Haemoglobin (MCH)	27 - 32	27 - 32	pg
Mean Cell Haemoglobin Concentration (MCHC)	300 - 370	300 - 370	g/L
Neutrophils	2 - 8	2 - 8	109/L
Lymphocytes	0.5 - 4.5	0.5 - 4.5	109/L
Monocytes	0.2 - 1.2	0.2 - 1.2	109/L
Eosinophils	0.1 - 0.7	0.1 - 0.7	109/L
Basophils	0.0 - 0.2	0.0 - 0.2	109/L

Osler's node

Osler's nodes are medical signs.

Features

• Tender
• Erythematous 
• Raised
• Lesions on the palms or soles 

 

Pathophysiology

• Antibody binds to antigen  
• Immune complexes form 
• Complexes are deposited in the tissues  
• Immune complexes trigger tissue inflammation 

 

Causes

• Infective endocarditis
• Systemic lupus erythematosus
• Marantic endocarditis
• Disseminated gonococcal infection
• Distal to infected arterial catheter

 

See also

• Osler's node

Janeway lesion

Janeway lesions are medical signs.

Features

• Non-tender
• Erythematous or haemorrhagic 
• Macular or nodular 
• Lesions on the palms or soles 
• Only a few millimeters in diameter

 

Pathophysiology

• Septic emboli reach the tissues and deposit bacteria
• Micro-abscesses form 
• Marked necrosis and inflammatory infiltrate
• Affects the dermis but not the epidermis

Causes

• Infective endocarditis

See also

• Osler's node

Acute abdomen

This refers to a potential presentation of a patient with acute-onset severe abdominal pain.

This presentation is very common. The diagnosis of acute abdominal pain is infamous in medicine due to the large size of the differential diagnosis and the number of medical and surgical emergencies which present this way.

 

Causes 

Gastrointestinal

• Appendicitis
• Colitis 
• Diverticulitis
• Gastroenteritis
• Gastrointestinal perforation  
• Inflammatory bowel disease
• Intestinal obstruction  
• Mesenteric lymphadenitis
• Peptic ulcer disease
• Perforated viscus  
• Strangulated hernia
• Volvulus
• Paediatric
• Intussusception
• Meckel's diverticulum 

 

Hepatobiliary

• Acute cholangitis    
• Acute cholecystitis
• Acute hepatitis
• Acute pancreatitis
• Cholelithiasis (gallstones)    
• Haematobilia 

 

Vascular

• Ischaemic colitis
• Mesenteric ischaemia 
• Ruptured aortic aneurysm 

 

Nephro/Urological

• Acute urinary retention
• Pyelonephritis
• Urinary tract infection (UTI)
• Urolithiasis

 

Andrological

• Testicular torsion

 

Gynaecological

• Endometriosis
• Mittelschmerz 
• Ovarian torsion  
• Ruptured ectopic pregnancy 
• Ruptured ovarian cyst   
• Salpingitis
• Tubo-ovarian abscess 

 

Musculoskeletal

• Muscle strain
• Psoas abscess
• Rib fracture 

Medical

• Hypercalcaemia
• Malaria 
• Cardiac pain
• Pericarditis  
• Myocardial infarction
• Pleuritic pain
• Pneumonia
• Porphyria  
• Sickle cell crisis 

 

Endocrinological

• Acute adrenal insufficiency
• Diabetic ketoacidosis 
• Phaeochromocytoma
• Thyrotoxicosis 

 

Neurological 

• Herpes zoster
• Lead poisoning  
• Syphilis / Tabes dorsalis 

 

Other infectious diseases

• Bornholm disease 
• Cholera
• Tuberculosis
• Typhoid fever 
• Yersinia

 

Must not be missed

• Perforated viscus  
• Acute pancreatitis
• Ruptured aortic aneurysm  
• Ruptured ectopic pregnancy 
• Ovarian torsion 
• Testicular torsion
• Myocardial infarction

Investigations

• For women of reproductive age, always pregnancy test, even if they deny any chance of pregnancy. 
• Glucose meter for diabetes mellitus
• Urine test strip to check for UTI
• Full blood count 
• Urine microscopy
• Ultrasound scan 
• Liver
• Abdomen 
• Plain x-ray imaging 
• Abdomen
• CT scan  
• Abdomen
• Diagnostic endoscopy

 

Management

If indicated:

• ABCD assessment 
• Cannulation 
• Analgesia for pain relief
• Oxygen therapy 
• Fluid resuscitation 
• Urinary catheterisation 
• NG tube feeding 
• Airway management
• Urgent surgery

Faltering weight

Gram stain

Gram staining is a method of staining bacteria to add colouration and facilitate visualisation under a microscope. 

 

Method

1. Gram-positive organisms can take up the first stain and retain it during discolourisation.
2. Gram-negative organisms can take up the first stain, but lose it during discolourisation.
3. There is a wash with a counterstain and this adds a second colour to the Gram-negative organisms.
4. This produces two different colours, which allows a microbiologist to differentiate Gram-positive from Gram-negative species.

 

Limitations

• Acid-fast bacteria are resistant to staining and then resistant to discolouration. They must be identified with a Ziehl–Neelsen stain. 

 

Origin

• Danish bacteriologist Hans Christian Gram invented this technique.