Differentials
Common
Pyrexial response to surgery
History
fever presenting in the first 48 hours, self-limiting
Exam
usually normal
1st investigation
- no initial test:
clinical diagnosis
Other investigations
- blood cultures:
negative
Urinary tract infection
History
dysuria, frequency, urgency, suprapubic pain, hematuria, indwelling urethral catheter, cloudy urine
Exam
suprapubic tenderness
1st investigation
- urinalysis:
positive for nitrites and leukocyte esterase
- urine culture:
detection of causative organism
Other investigations
Wound infection
History
pain at the site of the wound, usually presents at least 48 hours postoperatively
Exam
wound erythema, tenderness, purulent discharge
1st investigation
- wound culture:
identification of causative organism
More
Other investigations
Pneumonia
History
cough, shortness of breath, pleuritic chest pain, long surgical time, prolonged endotracheal intubation
Exam
bronchial breath sounds, crepitations, poor air entry
1st investigation
- CBC:
elevated white cell count
- chest x-ray:
unilateral infiltration, consolidation, effusions, cavitation
- sputum cultures:
identification of causative organism
Other investigations
- blood cultures:
identification of causative organism
More
Superficial thrombophlebitis
History
pain at the site of line or catheter insertion, especially central venous catheters
Exam
catheter site erythema and tenderness, purulent material may be expressed from the venous catheter exit site
1st investigation
- no initial test:
clinical diagnosis
Other investigations
- culture of purulent discharge:
identification of causative organism
More - ultrasound:
abscess or thrombosis
Catheter-associated intravascular infection
History
presence of intravascular catheters, especially central venous catheters
Exam
tachycardia, hypotension
1st investigation
- CBC:
elevated white cell count
- blood cultures:
identification of causative organism
More
Other investigations
Abdominal abscess
History
new-onset abdominal pain, abdominal bloating, vomiting, constipation
Exam
spiking fever, abdominal mass, focal tenderness
1st investigation
- CBC:
elevated white cell count
- blood cultures:
identification of causative organism
- abdominal CT scan:
detection of intra-abdominal abscess
More
Other investigations
Foreign body infection
History
history of implantation of orthopedic implants, endovascular devices, grafts and stents; swelling, erythema or pain at the site of prosthesis
Exam
low-grade fever, decreased range of motion of prosthetic joint; cardiac murmur, Janeway lesions, Osler nodes, Roth spots in infectious endocarditis
1st investigation
- CBC:
elevated white cell count
- blood cultures:
identification of causative organism
Other investigations
- culture of wound discharge:
identification of causative organism
- synovial fluid culture:
identification of causative organism
- tissue culture:
identification of causative organism
- x-ray of joint prosthesis:
implant loosening
More - technetium-methylene diphosphonate scintigraphy with leukocyte scan:
detection of prosthetic joint infection
Clostridium difficile colitis
History
diarrhea, abdominal pain, and distention, systemic antibiotic use in the preceding week
Exam
abdominal distension, ileus
1st investigation
- stools for C difficile cytotoxin:
positive
Other investigations
- CBC:
white cell count elevated. White cell count may be as high as 30,000-50,000/microliter in fulminant colitis.
Sepsis
History
symptoms of localized infection, nonspecific symptoms include fever or shivering, dizziness, nausea and vomiting, muscle pain, feeling confused or disoriented; may be history of risk factors e.g. immunosuppression, pregnancy or postpartum period, frailty, recent surgery or invasive procedures, intravenous drug use or breach of skin integrity
Exam
tachycardia, tachypnea, hypotension, fever (>100.4ºF [>38ºC]) or hypothermia (<96.8ºF [<36ºC]), prolonged capillary refill, mottled or ashen skin, cyanosis, low oxygen saturation, newly altered mental state, reduced urine output
1st investigation
- blood culture:
may be positive for organism
More - serum lactate:
may be elevated; levels >18 mg/dL (>2 mmol/L ) associated with adverse prognosis; even worse prognosis with levels ≥36 mg/dL (≥4 mmol/L)
More - CBC with differential:
WBC count >12×10⁹/L (12,000/microliter) (leukocytosis); WBC count <4×10⁹/L (4000/microliter) (leukopenia); or a normal WBC count with >10% immature forms; low platelets
More - C-reactive protein:
elevated
- blood urea and serum electrolytes:
serum electrolytes may be deranged; blood urea may be elevated
- serum creatinine:
may be elevated
More - liver function tests:
may show elevated bilirubin, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and gamma-glutamyl transferase
More - coagulation studies:
may be abnormal
- ABG:
may be hypoxia, hypercapnia, elevated anion gap, metabolic acidosis
Other investigations
- ECG:
may show evidence of ischemia, atrial fibrillation, or other arrhythmia; may be normal
More - chest x-ray:
may show consolidation; demonstrates position of central venous catheter and tracheal tube
- urine microscopy and culture:
may be positive for nitrites, protein or blood; elevated leukocyte count; positive culture for organism
- sputum culture:
may be positive for organism
- lumbar puncture:
may be elevated WBC count, presence of organism on microscopy and positive culture
More
Hematoma
History
pain, swelling, or pressure at site of operation; vomiting, severe headache, seizures in raised intracranial pressure due to subdural or epidural hematoma
Exam
fever, fluctuant swelling at wound site; hypotension, coma due to raised intracranial pressure in subdural or epidural hematoma; rarely compartment syndromes of operated compartment (most likely after orthopedic trauma surgery)
1st investigation
- ultrasound:
hypoechoic fluid collection
Other investigations
- compartment pressure measurement:
variable; differential pressure within 20-30 mmHg of the diastolic pressure is considered a strong indicator for fasciotomy
- CT scan head:
subdural or epidural hematoma
Deep venous thrombosis
History
swelling and pain of the affected limb, fever presenting in the second postoperative week or later
Exam
asymmetric lower extremity swelling, calf tenderness, palpable thrombosed vein, Wells score ≥2 indicates high risk of deep venous thrombosis
1st investigation
- lower extremity duplex ultrasound:
detection of thrombosis
Other investigations
Pulmonary embolism
History
shortness of breath, pleuritic chest pain, lower extremity swelling, and pain on the affected limb if an associated deep vein thrombus is present
Exam
fever, tachycardia, hypoxemia, hypotension, modified Wells or Geneva score >4
1st investigation
- arterial blood gas:
hypoxia and hypocapnia
- CT pulmonary angiography:
detection of embolus
- chest x-ray:
band atelectasis, elevation of hemidiaphragm, prominent central pulmonary artery, oligemia at site of embolism
More - ECG:
atrial arrhythmias, right bundle branch block, inferior Q waves, precordial T-wave inversion and ST segment changes suggest poor prognosis
More
Other investigations
- ventilation-perfusion (V/Q) scan:
pulmonary embolism likely when an area of ventilation is not perfused
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Uncommon
Drug fever
History
fever typically appearing within 7 days of the causative medication being started, history of causative drug (e.g., hydroxyurea, propylthiouracil, iodides, heparin, allopurinol, immune globulins, salicylates, phenytoin, hydralazine, procainamide, furosemide, and thiazide diuretics)
Exam
rash
1st investigation
- discontinue causative medications:
resolution of the fever and rash
More
Other investigations
Myocardial infarction
History
central chest pressure, squeezing, or heaviness; radiation to jaw or upper extremities; associated nausea, vomiting, dyspnea, dizziness, weakness; risk factors: smoking, age (males >45 years, females >55 years), family history of premature coronary artery disease, hypertension, hyperlipidemia, diabetes, stroke, or peripheral arterial disease
Exam
jugular venous distention, S4 gallop, holosystolic murmur (mitral regurgitation), bibasilar rales; hypotensive, tachycardic, bradycardic, or hypoxic depending on severity of ischemia
1st investigation
- ECG:
ST-elevation myocardial infarction (MI): ST segment elevation of >1 mm in 2 or more anatomically contiguous leads or new left bundle branch block; non-ST elevation MI: nonspecific; ST segment depression or T-wave inversion
- CXR:
normal or signs of heart failure, such as increased alveolar markings
- cardiac enzymes:
elevated
Other investigations
- B-type natriuretic peptide:
>99th percentile of normal
- coronary angiography:
critical occlusion of a coronary artery or evidence of coronary artery narrowing
Stroke
History
weakness, vision loss, aphasia
Exam
ataxia, visual field defect, focal weakness, or cranial nerve deficits
1st investigation
- head CT scan:
hemorrhagic stroke: enhancing lesion; ischemic stroke: hypoattenuation (darkness) of the brain parenchyma; loss of gray matter-white matter differentiation, and sulcal effacement; hyperattenuation (brightness) in an artery indicates clot within the vessel lumen
More - head MRI scan:
ischemic stroke: acute ischemic infarct appears bright on diffusion-weighted imaging; at later stages, T2 images may also show increased signal in the ischemic territory
Other investigations
Alcohol withdrawal
History
prior history of alcohol abuse and abrupt stop due to hospitalization, tremors, nausea, confusion, hallucinations
Exam
fever, delirium, tremors, tachycardia
1st investigation
- no initial test:
clinical diagnosis
Other investigations
Fat embolism
History
major trauma or major orthopedic surgery, onset is 48 to 72 hours postoperatively
Exam
petechial rash, hypoxemia
1st investigation
- CXR:
diffuse interstitial pattern suggestive of acute respiratory distress syndrome
More - chest CT:
diffuse ground glass appearance
Other investigations
Transfusion reaction
History
onset during or up to 1 hour after blood transfusion, dyspnea, anxiety
Exam
tachycardia, hypotension, wheezing
1st investigation
- inspection of plasma in centrifuged, anticoagulated venous blood sample:
pink red within first few hours of hemoglobinemia
- inspection of centrifuged urine:
clear red in hemoglobinemia
Other investigations
- ABO typing:
may be incompatible with recipient
- direct antiglobulin (Coombs) test:
Immunoglobulin G anti A, anti B, or anti AB detected on circulating red cells
Transplant rejection
History
history of organ transplantation, malaise, oliguria in kidney rejection, shortness of breath in lung rejection, jaundice and bleeding in liver rejection; symptoms can be hyperacute (onset within minutes or hours) or acute (onset within weeks)
Exam
jaundice and ecchymoses (liver)
1st investigation
- tissue biopsy:
shows characteristic features of transplant rejection
Other investigations
Toxic shock syndrome
History
antecedent wound infection, confusion, malaise, diarrhea, vomiting, respiratory distress
Exam
diffuse macular desquamating erythroderma, high-grade fever, hypotension, tachycardia, poor capillary refill, tachypnea, acute mental confusion, decreased urine output, hypothermia
1st investigation
- CBC:
white cell count >12,000/microliter or <4000/microliter
- blood cultures:
identification of Staphylococcus aureus or group A beta-hemolytic Streptococcus
More
Other investigations
Ischemia of operated tissue
History
rapid onset of severe pain in affected region, fever in immediate postoperative period
Exam
tachycardia, hypotension
1st investigation
- CBC:
leukocytosis, anemia, hemoconcentration
- arterial blood gas:
acidosis
- blood lactate:
elevated
- diagnostic laparotomy:
necrosis, gangrene of operated tissue
Other investigations
- angiography:
defect of the supplying vessel
Gout exacerbation
History
acute onset of severe joint tenderness 1 to 17 days postoperatively; usually affects the metatarsophalangeal joint, knees or ankles
Exam
monoarticular or oligoarticular joint swelling, warmth, and redness
1st investigation
- joint aspiration:
WBCs >2000/microliter; needle-shaped, negatively birefringent crystals
More
Other investigations
Pseudogout exacerbation
History
acute onset of severe joint tenderness 1 to 17 days postoperatively; the knee and wrist joints are most commonly affected
Exam
monoarticular or oligoarticular joint swelling, warmth, and redness
1st investigation
- joint aspiration:
WBCs >2000/microliter; rhomboid- or pleomorphic-shaped, weakly positively birefringent crystals
More
Other investigations
Acute pancreatitis
History
epigastric pain radiating to the back, nausea, vomiting
Exam
varying degrees of abdominal tenderness, usually worse in the epigastric region; tachycardia
1st investigation
Other investigations
- abdominal ultrasound:
may see ascites, gallstones, dilated common bile duct, and enlarged pancreas
More - CT scan of abdomen with oral and intravenous (IV) contrast:
may show pancreatic inflammation, peripancreatic stranding, calcifications, or fluid collections; confirms or excludes gallstones
More - MRI/magnetic resonance cholangiopancreatography (MRCP):
findings may include stones, tumors, diffuse or segmental enlargement of the pancreas with irregular contour and obliteration of the peripancreatic fat, necrosis, or pseudocysts
More
Acalculous cholecystitis
History
parenteral nutrition, severely ill patients
Exam
severe right upper quadrant pain radiating to the right side, tenderness, positive Murphy sign
1st investigation
- CBC:
elevated white cell count
- ultrasonography:
thickened gallbladder, absence of stones, emphysematous gallbladder
- liver function tests:
hyperbilirubinemia, alkaline phosphatase, and a mild increase in serum aminotransferases
Other investigations
Seroma
History
painless wound swelling
Exam
nontender fluctuant swelling at wound site
1st investigation
- ultrasound:
anechoic fluid collection
Other investigations
Malignant hyperthermia
History
sudden onset of fever within 12 hours of administration of inhalation anesthetic or succinylcholine
Exam
fever >104°F (40°C), muscle rigidity, hemodynamic instability
1st investigation
- serum electrolytes and arterial blood gas:
metabolic acidosis
- discontinuation of inhaled anesthetic:
partial resolution of symptoms
- therapeutic trial of dantrolene:
resolution of symptoms
Other investigations
Hyperthyroidism exacerbation
History
history is usually known, heat intolerance, sweating, weight loss, palpitations
Exam
goiter, ophthalmopathy (in Graves disease)
1st investigation
- thyroid-stimulating hormone:
low
- serum free thyroxine:
elevated
- serum free or total triiodothyronine:
elevated
Other investigations
Pheochromocytoma exacerbation
History
history is usually known, headache, palpitations, diaphoresis, episodic pallor
Exam
hypertension, orthostatic hypotension
1st investigation
- serum free metanephrines and normetanephrines:
elevated
- 24-hour urine collection for catecholamines, metanephrines, normetanephrines, and creatinine:
elevated
More - plasma catecholamines:
may be elevated
Other investigations
- MRI of abdomen and pelvis:
detected as hyperintense lesions to the liver on T2-weighted images
Adrenal crisis
History
history is usually known, patients are acutely ill with symptoms such as vomiting, dizziness, and hypotension
Exam
physical orthostasis, hyperpigmentation
1st investigation
- serum cortisol:
low
- serum adrenocorticotropic hormone:
elevated in primary adrenal insufficiency
Other investigations
Transfusion-related infection
History
chills, rigor in bacterial or West Nile virus infection
Exam
hypotension, tachycardia, poor capillary refill, tachypnea, acute mental confusion, decreased urine output, hypothermia in bacterial infection
1st investigation
- CBC:
elevated white cell count depending on underlying infection
- blood cultures:
identification of bacteria
- enzyme immunoassay for West Nile virus:
positive in West Nile virus infection
Other investigations
Underlying malignancy
History
fever, chills, weight loss, history suggests location of primary tumor (e.g., headache or mental status changes suggests brain tumor, cough suggests lung tumor)
Exam
hepatosplenomegaly, rales, or dullness to percussion
1st investigation
- CT of suspected area:
tumor
Other investigations
- biopsy of suspicious lesion:
malignant cells
Meningitis post neurosurgery
History
history of neurosurgery, headache, neck stiffness, photophobia
Exam
hemorrhagic rash, Kernig sign
1st investigation
- CBC:
elevated white cell count
- lumbar puncture:
elevated white cell count, identification of causative organism
More
Other investigations
Subarachnoid hemorrhage post neurosurgery
History
fever within first 48 hours of neurosurgery, severe occipital headache, photophobia, nausea, vomiting
Exam
decreased conscious level, intraocular hemorrhage
1st investigation
- CT head:
hyperdense areas in the basal cisterns, major fissures and sulci
Other investigations
- lumbar puncture:
bloody cerebrospinal fluid (xanthochromia)
Otitis media post ENT surgery
History
otalgia, history of head and neck surgery
Exam
bulging tympanic membrane, myringitis
1st investigation
- no initial test:
clinical diagnosis
Other investigations
- tympanometry:
low compliance
- tympanocentesis and culture:
identification of causative organism
Sinusitis post nasogastric tube insertion
History
history of prolonged nasogastric tube insertion, nasal congestion, and discharge
Exam
sinus tenderness
1st investigation
- no initial test:
clinical diagnosis
Other investigations
- CT scan of the sinus:
mucosal thickening of sinuses, air fluid levels, sinus opacification
Sialadenitis
History
pain, dysphagia
Exam
unilateral facial swelling over parotid region, exudates of pus from salivary gland opening
1st investigation
- culture of exudate from duct:
identification of causative organism
- facial radiographs:
sialoliths
Other investigations
- CT of affected gland:
sialoliths
More
Cavernous sinus thrombosis post ENT or neurosurgery
History
history of head and neck surgery or neurosurgery, headache, lethargy, rapid onset of acute toxic symptoms
Exam
periorbital edema, chemosis and proptosis, lateral gaze palsy, ophthalmoplegia, hypotension, tachycardia
1st investigation
- CBC:
marked polymorphonuclear leukocytosis; anemia
- blood culture:
identification of causative organism in patients with sepsis
- microscopy and culture of suppurative fluid or tissue from primary infectious source:
identification of causative organism
- contrast-enhanced high-resolution CT of head:
abnormal filling defects together with lateral convexity of the cavernous sinuses
Other investigations
- contrast-enhanced MRI of head:
expansion of the cavernous sinuses, convex bowing of lateral walls, increased dural enhancement; sphenoid sinus pathology may be present
More
Osteomyelitis following orthopedic surgery
History
history of recent orthopedic surgery, gradual onset with bone pain, warmth and swelling, fever
Exam
fever, tenderness, erythema, warmth, swelling
1st investigation
- CBC:
elevated white cell count
- erythrocyte sedimentation rate:
elevated (>70 mm/hour)
- CRP:
elevated (>95.2 nanomols/L [>10 mg/L])
- plain radiograph:
infected areas typically appear dark; soft tissue swelling, periosteal thickening, and focal osteopenia may be apparent; lytic changes are late changes
- blood cultures:
may be positive
- bone biopsy:
may be positive; performed if debridement surgery takes place; antibiotic treatment will be directed by results of cultures
Other investigations
- MRI:
infected areas typically appear with decreased signal intensity on T1-weighted images, and increased signal intensity on T2-weighted images
- fluorodeoxyglucose positron emission tomography/ single photon emission computed tomography:
increased uptake of radioactive injectate in infected sites
More
Infective endocarditis following cardiac surgery
History
history of prosthetic valve surgery, fever, night sweats, malaise, weight loss, anorexia, myalgia, headache, arthralgia, shortness of breath
Exam
cardiac murmur, Janeway lesions, Osler nodes, Roth spots
1st investigation
- blood cultures:
identification of causative organism
More - echocardiogram:
valvular, mobile vegetations in infectious endocarditis
Other investigations
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