Complication	Clinical signs	Diagnostics*
Skin and soft tissue
Infectious
Abscess	Fluctuance, purulence, erythema, pain, induration	US or CT to evaluate underlying structures and retained products, with or without Gram stain or culture
Cellulitis	Erythema, induration, pain, warmth	Clinical diagnosis
Necrotizing soft tissue infection	Erythema, edema, pain out of proportion to examination findings, crepitus, rapid progression	AST, creatine kinase, lactate, C-reactive protein; surgical exploration with wound and tissue cultures; CT or MRI if diagnosis is unclear
Septic thrombophlebitis	Linear erythema, pain	Duplex US to evaluate for thrombus
Noninfectious
Contact dermatitis	Erythema, pruritus, edema	Clinical diagnosis
Hyper/hypopigmentation	Hyperpigmented macules	Clinical diagnosis
Lesions from pathologic skin picking (cocaine, methamphetamine)	Repetitive and compulsive picking of skin	Clinical diagnosis
Phlebitis/thrombophlebitis	Venous-associated pain, tenderness, erythema	Duplex US to evaluate for thrombus
Vasculitis (cocaine)	Levamisole-associated contamination: purpura/necrosis of ears, cheeks, nose, extremities	Perinuclear antineutrophil cytoplasmic antibodies, antimyeloperoxidase
Venous insufficiency	Edema (hands, feet/legs), hyperpigmentation, ulceration, decreased peripheral pulses, delayed capillary refill	Duplex US, echocardiography
Pulmonary
Infectious
Aspiration pneumonia	Abrupt-onset dyspnea, diffuse crackles, fever, altered mental status	Chest radiography if indicated
Community-acquired pneumonia	Cough, dyspnea, sputum production, fever, pleurisy	Chest radiography if indicated, sputum Gram stain and culture, urine Streptococcus pneumoniae antigen, legionella if admitted
Pulmonary tuberculosis	Fever, cough, hemoptysis, malaise, anorexia, weight loss	Chest radiography, sputum for acid-fast bacilli, culture, nucleic acid amplification tests, interferon-gamma release assay, or tuberculin skin test
Septic pulmonary embolism	Fever, cough, and dyspnea, with or without murmur or peripheral stigmata of endocarditis	Chest radiography, echocardiography
Noninfectious
Asthma	Intermittent wheezing, dyspnea, cough	Pulmonary function tests
Bullous emphysema	Progressive dyspnea, cough, fatigue	Chest imaging, pulmonary function tests
Foreign body granulomatosis	Progressive dyspnea, cough, fatigue	Chest imaging, pulmonary function tests
Noncardiogenic pulmonary edema (opioids)	Acute shortness of breath, mental status change, respiratory depression, hypoxemia	Chest radiography
Pulmonary embolism	Acute shortness of breath, tachypnea, tachycardia, palpitations	d-dimer test, CT with pulmonary angiography or ventilation-perfusion scan
Cardiovascular
Infectious
Endocarditis	Fever, malaise, flulike illness, pleuritic chest pain, back pain, palpitations, Osler nodes, Janeway lesions, Roth spots, splinter hemorrhages	Transesophageal echocardiography, serial blood cultures, complete blood count
Septic emboli	Right-sided: see septic pulmonary embolism; left-sided: neurologic deficits, splinter hemorrhages, Roth spots, Janeway lesions	Transesophageal echocardiography, serial blood cultures, complete blood count
Noninfectious
Cardiomyopathy	Left ventricular systolic dysfunction, dyspnea on exertion, orthopnea, paroxysmal nocturnal dyspnea, edema	Echocardiography
Dysrhythmias	Variable; chest pain, palpitations, nausea, diaphoresis	Electrocardiography
Myocarditis/myocardial ischemia (cocaine)	Severe retrosternal chest pain, nausea, diaphoresis	Electrocardiography changes, abnormal echocardiography findings, elevated serum troponin I, occasional coronary artery occlusion
Mycotic aneurysms	Tender, enlarging, pulsatile mass; femoral vein most commonly affected	Doppler US, CT, or magnetic resonance angiography
Post–infectious endocarditis valvular heart disease	Heart failure, atrial fibrillation, pulmonary hypertension, dilated cardiomyopathy	Echocardiography
Musculoskeletal
Infectious
Epidural abscess	Back pain and local tenderness, fever, late neurologic compromise	MRI with contrast media, then CT-guided biopsy
Osteomyelitis	Musculoskeletal pain and fever, with or without overlying skin/soft tissue infection	MRI with contrast media (preferred) or bone scintigraphy, bone biopsy
Pyomyositis	Deep, aching muscle pain	MRI with contrast media, CT with contrast media, or US
Tetanus	Muscle spasms, stiffness, pain, fever, seizures	Clinical diagnosis
Noninfectious
Rhabdomyolysis (cocaine, methamphetamine)	Myalgias, swelling, weakness, and brown or red urine, with or without fever, abdominal pain, nausea/vomiting	Creatine kinase, creatinine, AST, ALT, urinalysis
Other
Infectious
Acute HIV	Fever, fatigue, myalgias, skin rash, headache, pharyngitis, cervical adenopathy	HIV RNA, HIV fourth-generation antibody/antigen test (may be negative in acute infection)
Brain abscess	Fever, headache, focal neurologic deficits	Lumbar puncture, neuroimaging
Hepatitis A, B, or C	Jaundice, fever, abdominal pain	Liver function tests, hepatitis serology or polymerase chain reaction test (if acute); liver ultrasonography
Meningitis	Fever, headache, neck stiffness, altered mental status	Lumbar puncture, neuroimaging
Splenic abscess	Fever, left upper abdominal pain, left shoulder pain (Kehr sign)	Ultrasonography or CT
Wound botulism	Symmetric neurologic deficits, responsiveness to stimuli, blurred vision, presence of a wound	Anaerobic wound culture, serum toxin assay
Noninfectious
Elevated transaminase/bilirubin levels (methamphetamine)	Asymptomatic	AST, ALT, bilirubin, albumin, hepatitis serologies
Perforated duodenal and gastric ulcers (cocaine)	Sudden, severe abdominal pain, tachycardia, hypotension	Upright abdominal radiography, CT or US
Splenic infarct (cocaine)	Asymptomatic or fever and left upper abdominal pain	US or CT