21.2 Osteomyelitis, Septic Arthritis & Acute Pediatric Genitourinary Emergencies
Key Takeaways
Kocher and Caird predictors help assess a painful hip. A high synovial white-cell count supports concern for bacterial arthritis, and joint fluid, cultures and the clinical course guide diagnosis and drainage.
For suspected bacterial arthritis at 6–48 months, PIDS/IDSA suggests empiric Kingella activity along with Staphylococcus aureus coverage. Osteomyelitis coverage broadens according to age, presentation and host risk.
Use radiographs first for suspected acute hematogenous osteomyelitis and MRI when advanced imaging is needed. Choose source control, oral transition and treatment duration by response, anatomy and pathogen.
High clinical suspicion for testicular or adnexal torsion warrants urgent surgical assessment. Doppler can assist an equivocal presentation. Preserved flow cannot exclude torsion.
In sickle cell ischemic priapism, obtain urgent corporal aspiration and intracavernosal phenylephrine with supportive care in parallel. In a boy with pelvic trauma and meatal blood, obtain urethral imaging before blind catheter placement.
Osteomyelitis, Bacterial Arthritis & Acute Pediatric Genitourinary Emergencies
Quick Answer: A febrile child with a painful hip and refusal to bear weight needs urgent assessment for bacterial arthritis and adjacent osteomyelitis. Interpret inflammatory markers and joint fluid alongside the exam. Cover S. aureus empirically and include K. kingae activity for suspected bacterial arthritis at 6–48 months. In acute testicular or adnexal torsion, involve the surgical team immediately. Painful ischemic priapism requires prompt urologic relief.
Bacterial Arthritis and Acute Hematogenous Osteomyelitis
Hematogenous osteomyelitis often localizes near a metaphysis and causes focal pain or refusal to use a limb. Acute bacterial arthritis (ABA) usually causes marked pain with passive motion and an effusion. These infections can coexist. Infection of the hip warrants urgent orthopedic evaluation because cartilage damage and femoral head ischemia are potential complications.
Interpret the Painful Hip
The original Kocher predictors for distinguishing bacterial hip arthritis from transient synovitis included a history of fever (the study used more than 38.5°C), refusal to bear weight, ESR at least 40 mm/hour and peripheral WBC above 12,000/µL. Caird's cohort identified additional predictive value for CRP above 2 mg/dL (20 mg/L). Use these findings to inform urgency. Estimated probabilities vary across populations, and a low count of predictors does not rule out infection in a young child with a less inflammatory presentation. Consider transient synovitis, adjacent bone or muscle infection, Lyme arthritis where epidemiologically plausible, trauma and inflammatory disease. Kocher derivation · Kocher validation · Caird prospective study
Obtain the Right Samples and Imaging
| Decision | Acute bacterial arthritis | Acute hematogenous osteomyelitis |
|---|---|---|
| Initial assessment | Obtain blood cultures before antibiotics when feasible, baseline CRP and radiographs of the joint and adjacent bones. Ultrasound detects a hip or shoulder effusion and can help guide aspiration. The effusion itself does not identify the cause. Reassess if initial imaging is negative but suspicion persists. | Obtain blood cultures before antibiotics when feasible, baseline CRP and plain radiographs. Early radiographs can be unrevealing but help assess fracture and other diagnoses. |
| Further testing | Send synovial cell count and differential, Gram stain and aerobic culture. A neutrophil-predominant count above 50,000/µL is common but overlaps with other causes, including Lyme arthritis. Preserve fluid for molecular testing when cultures are unrevealing, especially for possible K. kingae. | When further imaging is needed, MRI is preferred to define bone and soft-tissue involvement, adjacent joint infection or abscess. Use the pediatric radiology protocol to decide on contrast. Discuss sampling of bone or associated purulent collections when it can establish the pathogen or guide source control. |
| Antibiotic timing and drainage | If clinically stable, collect joint fluid before empiric antibiotics when feasible under close observation. If ill-appearing or rapidly worsening, start treatment promptly after blood cultures if possible. Do not wait for aspiration. Urgent orthopedic evaluation guides aspiration, arthroscopic drainage or open surgery according to site, findings and response. | Give prompt antibiotics in an ill-appearing or rapidly worsening child. Sepsis or rapid progression can require urgent operative source control. In a stable child, the guideline conditionally favors drainage of a substantial abscess greater than 2 cm. Specialist-directed diagnostic sampling may precede antibiotics in a carefully observed stable child. |
PIDS/IDSA pediatric bacterial arthritis guideline · PIDS/IDSA pediatric hematogenous osteomyelitis guideline
Select Empiric Coverage and Reassess
- Staphylococcal coverage: Include activity against S. aureus for both syndromes. Cefazolin is an example where MSSA coverage is suitable. Severity, prior MRSA and local susceptibility guide MRSA coverage. Vancomycin is a common option in severe disease when MRSA is a concern. Clindamycin is an option in selected cases with adequate susceptibility.
- Kingella: For suspected ABA at 6–48 months, the 2023 guideline conditionally suggests coverage for K. kingae. Vancomycin and clindamycin lack adequate activity. If one of those drugs is needed for MRSA, a cephalosporin such as ceftriaxone can supply Kingella coverage. Aerobic culture can identify Kingella, especially when the specimen is processed appropriately, and molecular testing can help when conventional methods are negative. The 2021 AHO guideline considers expanded empiric coverage when age, presentation, risk factors or response suggest organisms such as Kingella. It does not apply the ABA age recommendation as a universal AHO combination regimen.
- Special hosts: Both PIDS/IDSA guidelines exclude neonates. Seek neonatal infectious disease input for coverage of organisms including S. aureus, group B streptococci and enteric gram-negative bacilli. In sickle cell disease, consider Salmonella along with S. aureus. In a sexually active adolescent with compatible arthritis, tenosynovitis or pustular lesions, evaluate for disseminated gonococcal infection. Obtain appropriate mucosal and disseminated-site testing and follow CDC's ceftriaxone-based guidance, with chlamydial treatment when infection has not been excluded. CDC gonococcal treatment guidance
Follow fever, pain, movement, CRP and culture results. For confirmed S. aureus bacteremia, obtain follow-up blood cultures to document clearance and reassess for an uncontrolled focus if cultures remain positive. IDSA/ESCMID pediatric bacteremia consensus Persistent fever, bacteremia or a rising CRP despite therapy should prompt reassessment for adjacent infection or inadequate source control. Consider MRI and further drainage as appropriate. Transition to an effective and tolerated oral agent after a satisfactory clinical response and with a feasible follow-up plan. Fixed IV days and an isolated CRP threshold are insufficient to determine readiness. For selected rapidly improving uncomplicated primary ABA without adjacent osteomyelitis, a total of 10–14 days can suffice. For uncomplicated, responsive AHO due to presumed or proven S. aureus, the guideline suggests 3–4 weeks total. Complicated disease, persistent infection and particular organisms can require longer therapy. PIDS/IDSA ABA treatment recommendations · PIDS/IDSA AHO treatment recommendations
Acute Genitourinary Emergencies
Acute Scrotal Pain
Testicular torsion twists the spermatic cord and threatens perfusion. Sudden severe unilateral pain, vomiting, an abnormal testicular lie and absent cremasteric reflex increase concern. In neonates the presentation can differ and may include swelling or discoloration. When suspicion is high, call urology immediately and arrange surgical exploration without waiting for imaging. Salvage declines with ischemia duration and degree of twist, so urgent evaluation remains indicated even when presentation is delayed. The team detorses and fixes a viable testis and generally fixes the contralateral testis when torsion is confirmed. Doppler can clarify equivocal cases if rapidly available. Early, partial or intermittent torsion can retain arterial flow.
TWIST assigns two points each for swelling and a hard testis and one point each for absent cremasteric reflex, nausea or vomiting, and a high-riding testis. It supports risk assessment. The original study and later validations used different strata, and performance varies with pubertal stage. Use the local pediatric pathway and the full exam.
| Alternative diagnosis | Findings and initial decision |
|---|---|
| Torsed appendix testis | Upper-pole tenderness or a blue dot may be present. When testicular torsion is excluded, supportive treatment is usually sufficient. |
| Epididymitis | Posterior tenderness, urinary symptoms or epididymal hyperemia can support it. In prepubertal children, assess for bacterial UTI rather than automatically prescribing antibiotics. Assess STI risk in adolescents and select testing and therapy accordingly. Persistent or recurrent symptoms warrant reevaluation. |
EAU pediatric acute scrotum guideline · TWIST derivation · TWIST validation · CDC epididymitis guidance
Adnexal Torsion and Paraphimosis
Sudden or intermittent unilateral pelvic pain with nausea or vomiting can indicate adnexal torsion, including in a patient without an ovarian mass. Pelvic ultrasound can support the diagnosis, but preserved Doppler flow does not exclude it. When suspicion persists, involve gynecology promptly for diagnostic laparoscopy and detorsion with ovarian preservation whenever possible, even if the ovary appears dark. ACOG adolescent adnexal torsion guidance
Paraphimosis is entrapment of a retracted foreskin behind the glans. Provide analgesia and use gentle sustained compression to reduce edema, then return the foreskin over the glans. Failed reduction or dark, ischemic tissue requires urgent surgical assessment. A dorsal slit may be needed. After recovery, teach replacement of a freely retractable foreskin after examination or hygiene. Pediatric paraphimosis pathway
Acute Ischemic Priapism in Sickle Cell Disease
A painful erection with rigid corpora and a softer glans suggests ischemic priapism. A persistent episode of about four hours or longer is an emergency. Cavernosal blood gas typically shows low oxygen tension, high carbon dioxide tension and acidosis. Typical ischemic values are pO₂ below 30 mmHg, pCO₂ above 60 mmHg and pH below 7.25.
Give analgesia and obtain urgent urology consultation for corporal aspiration and intracavernosal phenylephrine, with or without irrigation. Monitor blood pressure and heart rate during phenylephrine use. Coordinate sickle cell care in parallel, giving maintenance IV fluid if NPO or replacing a documented deficit, and oxygen for hypoxemia. Avoid ice and hyperhydration in sickle cell disease. The AUA/SMSNA guideline advises against exchange transfusion as primary therapy and against delaying local treatment for systemic therapy. Involve hematology for separate transfusion indications or perioperative planning. AUA/SMSNA priapism guidance
Pediatric Renal and Urethral Trauma
Consider renal injury after significant blunt flank trauma or deceleration. Hematuria supports concern, but its absence does not exclude major injury. In a stable child with suspected significant renal injury, contrast-enhanced CT with immediate and delayed images helps stage injury and assess for collecting-system leakage. The EAST/Pediatric Trauma Society guideline favors nonoperative care for stable blunt renal injuries of all grades. For stable grade III–V injury with ongoing or delayed bleeding, consider angioembolization in preference to open surgery. Instability despite resuscitation or specific anatomy such as ureteropelvic junction avulsion requires urgent specialist intervention. Plan follow-up imaging according to injury and protocol. AUA recommends follow-up CT after 48 hours for deep grade IV–V injuries, or when signs of complications warrant it. Arrange blood pressure follow-up for post-traumatic hypertension. EAST/PTS pediatric renal trauma guideline · AUA urotrauma guidance
In boys with blood at the urethral meatus after pelvic trauma, obtain a retrograde urethrogram before blind catheter passage. Pelvic or perineal trauma with bruising, inability to void or other findings can also raise suspicion. Involve pediatric urology for suspected injury in either sex and determine safe drainage. Suprapubic drainage may be necessary when the urethra is disrupted. EAU pediatric urological trauma guideline
A 19-month-old has fever to 39.1°C, refuses to bear weight and has severe pain with passive movement of the left hip. WBC is 14,200/µL, ESR 52 mm/hour and CRP 4.6 mg/dL. Ultrasound shows an effusion. After blood cultures, aspiration yields cloudy fluid with 78,000 white cells/µL, 88% neutrophils and a negative Gram stain. He is ill-appearing, and the local empiric protocol covers MRSA in severe presentations. What is the best next step?
Involve orthopedics urgently to determine further drainage and start IV therapy covering MRSA and Kingella, such as vancomycin with ceftriaxone
Observe on ibuprofen for transient synovitis until cultures return
Arrange joint drainage and use clindamycin alone while awaiting molecular testing
Discharge on oral cephalexin and repeat hip ultrasound in three days
A 14-year-old has had three episodes of right scrotal pain that resolved on their own. Today the pain persists. The testis has a transverse lie. Doppler shows arterial flow in both testes, but the examiner cannot assess the spermatic cord. What is the next step?
Discharge with analgesia because bilateral arterial flow excludes torsion.
Contact urology immediately because the findings still raise concern for torsion and may warrant exploration.
Start oral antibiotics for epididymitis and arrange a routine follow-up visit.
Repeat Doppler the following morning before asking urology to evaluate the child.
A 13-year-old with HbSS has a painful rigid erection for 5.5 hours and a soft glans. Cavernosal blood gas shows pH 7.14, pCO₂ 68 mmHg and pO₂ 24 mmHg. He is euvolemic and normoxic, and his hemoglobin is at baseline. Which initial management follows AUA/SMSNA guidance?
Start exchange transfusion and wait for completion before local treatment
Apply ice and observe for another four hours after oral pseudoephedrine
Provide analgesia and urgent urologic aspiration and intracavernosal phenylephrine, with supportive care in parallel
Give a simple red-cell transfusion to raise hemoglobin above 11 g/dL as first-line detumescence therapy
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