Brock Syndrome

8/7/2019 Brock Syndrome

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introduction

Background

Right middle lobe syndrome (RMLS) generally refers to atelectasis in the right middle lobe of the

lung. It is caused by various etiologies and has no consistent clinical definition. Right middle lobe

syndrome is characterized by a wedge-shaped density that extends anteriorly and inferiorly

from the hilum of the lung, which is best visualized using lateral chest radiography.

Lateral view chest radiograph of Media file 1 showing a wedge-shaped density extending from the

hilum anteriorly and inferiorly.

This condition is most common in children with a history of asthma or atopy. Although the

mechanism by which asthma leads to lobar atelectasis is unknown, associated inflammation,

bronchospasm, and secretions that cause mucus plugging are likely major contributors.


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Management is determined by etiology, and most patients respond to medical therapy alone.

P athophysiology

Certain anatomical characteristics make the right middle lobe susceptible to transient obstruction as

a result of inflammation or edema. The narrow diameter of the lobar bronchus and acute take-

off angle create poor conditions for drainage. Relative anatomical isolation of the middle lobe

and poor collateral ventilation decrease the chance of reinflation once atelectasis occurs.

Bronchial obstruction can result from extrinsic compression as in hilar lymphadenopathy or

tumor of neoplastic origin; however, atelectasis in children usually results from a process such

as asthma-associated edema and inflammation. Foreign body aspiration into the right middle

lobe orifice can also predispose to collapse of the lobe.

FrequencyUnited States

The precise incidence in children is unknown. Right middle lobe syndrome is widely underdiagnosed

and frequently unrecognized.

Mortality/Morbidity

Severity in children ranges from mild atelectasis and scarring of no consequence to severe

bronchiectasis requiring surgical resection.

Sex

Right middle lobe syndrome has been said to occur twice as often in girls than in boys; however,

large epidemiologic studies are lacking.

Age

Symptoms begin in early childhood, usually in children aged 1-2 years. Symptom frequency

decreases in later childhood, but the interval between onset of symptoms and diagnosis widely

varies.

Clinical

History

y The most common symptoms in right middle lobe syndrome (RMLS) include the following:

o P ersistent or recurrent cough

o Intermittent wheezing

o Dyspnea


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o H istory of recurrent or chronic pneumonia (May often be a misinterpretation of the

radiographic findings)

y In many cases, these respiratory symptoms are refractory to normal treatment.

y At least half of the patients report a history of asthma or atopy, and one third report a family

history of atopy.

y Less frequently reported symptoms, which may be indicative of chronic disease with

suppurative complications, include the following:

o Hemoptysis

o Low-grade fever

o Fatigue

o W eight loss

o Chest pain

P hysical

y Right middle lobe syndrome is essentially a radiographic diagnosis, and physical findings widely

vary.

y Auscultation of the lungs may reveal a fine wheeze, rales, or diffuse rhonchi, ranging from

decreased aeration and dullness to percussion in the region of the right middle lobe. The right

middle lobe is anterior, best heard at the nipple. The medial segment is located medial to the

nipple; the lateral segment is lateral to the nipple. Failure to listen to this area results in failure

to hear the right middle lobe.

y Clubbing is rarely found in patients with advanced disease.

Causes

y Intra-airway origin

o In children, right middle lobe syndrome is usually secondary to primary ventilation

disorders. Chronic inflammation of the airways, which contributes to atelectasis of the

right middle lobe, is present. A paucity of collateral ventilation is observed in children

and serves to prevent reinflation.

o P rimary disorders of ventilation include the following:

Asthma

Bronchopulmonary dysplasia

Chronic pneumonia or bronchitis

Cystic fibrosis


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O ther chronic lung diseases caused by aspiration or gastroesophageal reflux

P rimary ciliary dyskinesia (immotile cilia syndrome)

o Airway foreign body aspiration

o Endobronchial tumors

o Mucous plugging, as from any of the above

o G ranulation tissue

y Extra-airway origin

o Extraluminal compression is caused by the following:

Cardiovascular anomalies

Congenital malformations such as situs inversus and other anatomical defects

such as anomalous branching or abnormal diameter, length, or structure of the

bronchi Lymphadenopathy of peribronchial nodes

Tumors

Traction diverticula of the esophagus

y Infectious etiologies

o W hether the infection is a cause of the collapse or a result of airway stasis and poor

clearance may not be clear.

o P rimary infectious etiology is more frequent in adults; however, one pediatric study

found that 50% of children with collapsed right middle lobe had an underlying bacterial

infection. [1 ]

o Infectious causes also increase in frequency among immunocompromised patients.

o Common bacterial causes in children include Streptococcus

pneumoniae and Haemophilus influenzae .

o Fungal causes include histoplasmosis, blastomycosis, and aspergillosis, which manifest

as allergic bronchopulmonary aspergillosis (A P BA).

o Mycobacteria, including My cobacterium tuberculosis , My cobacterium avium-

intracellulare , and My cobacterium fortuitum have also been identified as causal agents.

o O ccurrence is mainly caused by extrinsic compression by hilar lymph nodes, which are

commonly observed in these infections as well as in fungal infections.

D ifferential D iagnoses

P neumonia


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O ther P roblems to Be Considered

Diagnosis of right middle lobe syndrome (RMLS) is mainly based on the presence of atelectasis of

the right middle lobe of long duration. Rule out acute right middle lobe pneumonia with repeat

chest radiography within 3-4 weeks of initial onset.

Workup

Laboratory Studies

The following studies may be indicated in right middle lobe syndrome (RMLS):

y P urified protein derivative (tuberculin) skin test

y CBC count and differential

y W estergren sedimentation rate

y Fungal serology by complement fixation and immune diffusion

y Q uantitative immunoglobulins panel

Imaging Studies

y Chest radiography with anteroposterior (A P ) and lateral views

o The classic finding of right middle lobe syndrome is a blurred right heart border and a

loss of volume in the right middle lobe (see Media file 1).

P osteroanterior chest radiograph demonstrating right middle lobe collapse and infiltrate. Note

blurred right heart border.


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o A wedge-shaped density extending from the hilum anteriorly and inferiorly is best

visualized on a lateral view (see Media file 2).

Lateral view chest radiograph of Media file 1 showing a wedge-shaped density extending from the

hilum anteriorly and inferiorly.

o Consolidation and infiltration are less commonly observed.

o Acute pneumonia should clear radiologically in 6-8 weeks.

y CT scanning

o If bronchiectasis is suspected, confirm diagnosis by performing high-resolution chest CT

scanning (see Media file 3), which carries less risk to younger patients or patients with

asthma than the seldom-used traditional bronchography.


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Chest CT scan showing extensive bronchiectasis of both medial and lateral segments of the right

middle lobe.

o H igh-resolution chest CT imaging is also helpful for follow-up medical therapy.

O ther Tests

y P ulmonary function tests ( P FTs) can be used to establish a previously unidentified asthmatic

component.

y Although findings on a baseline forced expiratory volume in one second (F EV1) may be normal, a

prebronchodilator and postbronchodilator study with 10-15% changes in F EV1 is diagnostic for

asthma.

P rocedures

y The value of bronchoscopy is 2-fold, as follows:

o It is immediately therapeutic in removing mucus and clearing the airway and can be

curative in some cases.

o It allows visualization of the airway and the ability to determine patency of the rightmiddle lobe bronchus and to discern whether endobronchial obstruction is the cause.

y Bronchoalveolar lavage can be concurrently performed to determine cellular elements in the

right middle lobe. It can also be used to assess the presence of infections by culturing and

staining for bacterial, fungal, viral, and mycobacterial pathogens.

Treatment


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Medical Care

y Long-term follow-up of children with right middle lobe syndrome (RMLS) shows that most

patients do not experience recurrent or persisting symptoms. This indicates that the first line of

treatment in all cases is conservative medical management, except in cases involving neoplastic

origin and those with bronchiectasis.

y Chest physical therapy and postural drainage are the hallmarks of therapy.

o Treat the asthmatic child with aggressive anti-inflammatory therapy such as inhaled

steroids. Consider systemic steroids. Guidelines for the diagnosis and management of

asthma have been established. [2 ]

o P rovide the patient with chest physical therapy and postural drainage. In unresponsive

patients or patients who have a predisposition to airway colonization, an appropriate

antibiotic, as determined by a bronchoalveolar lavage (BAL) culture, should be added totheir regimen.

y P atients with fungal infections (eg, histoplasmosis) or tuberculous infections who have hilar

adenopathy and complete blockage of their right middle lobe should be treated aggressively.

The addition of systemic corticosteroids may be necessary.

Surgical Care

y Lobectomy

o Lobectomy is indicated in cases of malignancy and bronchiectasis that are unresponsive

to medical therapy.

o O nly perform lobectomy when right middle lobe syndrome is associated with systemic

symptoms such as failure to thrive, persistent cough, and recurrent fever or when

chronic infection threatens the remainder of the lung.

y Bronchography: Avoid bronchography because of potential risks to the patient unless surgery is

seriously considered; therefore, always explore high-resolution CT imaging as an alternative.

Medication

The role of antibiotic therapy in the treatment of right middle lobe syndrome (RMLS) is not well

studied. Antibiotics are usually administered during acute exacerbations and when

bronchiectasis is well established. In this latter instance, long-term rotation of antibiotics (ie, 3

weeks on and 1 week off, then change antibiotic) is advocated. Base the choice of antibiotic on

culture and sensitivity results of either sputum or bronchoaveolar lavage (BAL) fluid. W hen this

is not available, select a broad-spectrum antibiotic to cover S pneumoniae, other streptococci, H


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influenzae, and M oraxella catarrhalis. Antibiotics can be orally or intravenously administered.

The use of nebulized antibiotics has not been studied in right middle lobe syndrome. Also see

Asthma for relevant treatment information.

Antibiotics

Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the

context of the clinical setting.

Cefuroxime (Ceftin, Zinacef)

Second-generation cephalosporin maintains gram-positive activity that first-generation

cephalosporins have; adds activity against P roteus mirabilis, H influenzae, Escherichia coli,

Klebsiella pneumoniae, and M catarrhalis. D osing

Adult

500 mg PO bid

750 mg to 2 g I V q8h

P ediatric

30 mg/kg/d PO divided q12h

75-150 mg/kg/d I V divided q8h; not to exceed 6 g/d

Interactions

Disulfiramlike reactions may occur when alcohol is consumed within 72 h after taking cefuroxime;

may increase hypoprothrombinemic effects of anticoagulants; may increase nephrotoxicity in

patients receiving potent diuretics such as loop diuretics; coadministration with aminoglycosides

increase nephrotoxic potential

Contraindications

Documented hypersensitivity

P recautions

P regnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

P recautions

Administer half dose if creatinine clearance is 10-30 mL/min and one-quarter dose if less than 10

mL/min; fungal and microorganism overgrowth may occur with prolonged therapy


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Cefpodoxime proxetil (Vantin)

Inhibits bacterial cell wall synthesis by binding to one or more of the penicillin-binding proteins;

bacteria eventually lyse because of ongoing activity of cell wall autolytic enzymes while cell wall

assembly is arrested.

D osing

Adult

100-400 mg PO q12h

P ediatric

10 mg/kg/d PO divided q12h; not to exceed 400 mg/d

Interactions

P robenecid increases effect; coadministration with furosemide and aminoglycosides increases

nephrotoxic effects

Contraindications


P recautions

P regnancy


P recautions

Caution with documented hypersensitivity to penicillins

Cefprozil (Cefzil)

Binds to one or more of the penicillin-binding proteins, which, in turn, inhibits cell wall synthesis and

results in bactericidal activity.

D osing

Adult

250-500 mg PO divided q12h

P ediatric

7.5-15 mg/kg/dose PO q12h

Interactions


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P robenecid increases effect; coadministration with furosemide and aminoglycosides increases

nephrotoxic effects

Contraindications


P recautions

P regnancy


P recautions

Adjust dosage in renal impairment

Erythromycin and sulfisoxazole (P

ediazole)Erythromycin is a macrolide antibiotic with a large spectrum of activity. Erythromycin binds to the

50S ribosomal subunit of the bacteria, which inhibits protein synthesis.

Sulfisoxazole expands erythromycin's coverage to include gram-negative bacteria. Sulfisoxazole

inhibits bacterial synthesis of dihydrofolic acid by competing with para-aminobenzoic acid.

D osing

Adult

400 mg erythromycin and 1200 mg sulfisoxazole PO q6h

P ediatric

40-50 mg/kg/d (erythromycin component) PO divided q6-8h; not to exceed 2 g/d of erythromycin or

6 g/d of sulfisoxazole

Interactions

Decreases clearance of terfenadine (recalled from US market) , cisapride and astemizole (recalled

from US market) , which may result in serious cardiac arrhythmias; decreases clearance of

cyclosporin, midazolam, phenytoin, triazolam, and theophylline; increases the toxicity of

warfarin and ergotamine

Contraindications

Documented hypersensitivity; hepatic impairment; concomitant administration of terfenadine,

cisapride, and astemizole; G -6-PD deficiency; infants


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C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if

benefits outweigh risk to fetus

P recautions

Caution in liver disease; G I adverse effects are common (administer doses pc); discontinue use if

nausea, vomiting, malaise, abdominal colic, or fever occur

Azithromycin (Zithromax)

Inhibits bacterial growth, possibly by blocking dissociation of peptidyl tRNA from ribosomes, causing

RNA-dependent protein synthesis to arrest.

D osing

AdultDay 1: 500 mg/d PO

Days 2-5: 250 mg/d PO

P ediatric

Day 1: 10 mg/kg PO once; not to exceed 500 mg/d

Days 2-5: 5 mg/kg PO qd; not to exceed 250 mg/d

Interactions

May increase toxicity of theophylline, warfarin, and digoxin; effects are reduced with

coadministration of aluminum and/or magnesium antacids; nephrotoxicity and neurotoxicity

may occur when coadministered with cyclosporine

Contraindications

Documented hypersensitivity; hepatic impairment; administration with pimozide

P recautions

P regnancy


P recautions

Site reactions can occur with I V route; bacterial or fungal overgrowth may result with prolonged

antibiotic use; may increase hepatic enzymes and cholestatic jaundice; caution in patients with

impaired hepatic function, prolonged Q T intervals, or pneumonia


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Clarithromycin (Biaxin)

Inhibits bacterial growth, possibly by blocking dissociation of peptidyl tRNA from ribosomes, causing

RNA-dependent protein synthesis to arrest.

D osing

Adult

250-500 mg PO q12h

P ediatric

15 mg/kg/d PO divided bid

Interactions

Toxicity increases with coadministration of fluconazole, astemizole (recalled from US market) ,

terfenadine (recalled from US market) , and pimozide; clarithromycin effects decrease and G I

adverse effects may increase with coadministration of rifabutin or rifampin; may increasetoxicity of anticoagulants, cyclosporine, tacrolimus, digoxin, omeprazole, carbamazepine, ergot

alkaloids, triazolam, and HMG CoA-reductase inhibitors; serious cardiac arrhythmias may occur

with coadministration of cisapride; plasma levels of certain benzodiazepines may increase,

prolonging CNS depression; arrhythmias and increase in Q Tc intervals occur with disopyramide;

coadministration with omeprazole may increase plasma levels of both agents

Contraindications

Documented hypersensitivity; coadministration of pimozide, astemizole, cisapride, and terfenadine

P recautions

P regnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if

benefits outweigh risk to fetus

P recautions

Coadministration with ranitidine or bismuth citrate is not recommended with CrCl


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Drug combination treats bacteria resistant to beta-lactam antibiotics. For children >3 months, base

dosing protocol on amoxicillin content. Due to different amoxicillin/clavulanic acid ratios in 250-

mg tab (250/125) vs 250 mg chewable-tab (250/62.5), do not use 250-mg tab until child weighs

>40 kg.

D osing

Adult

250-500 mg PO q8h

P ediatric

3 months: if using 200 mg/5 mL or 400 mg/5 mL susp, 45 mg/kg/d PO divided q12h; if using

125 mg/5 mL or 250 mg/5 mL suspension, 40 mg/kg/dPO

divided bid for 7-10 d>40 kg: Administer as in adults

Interactions

Coadministration with warfarin or heparin increases risk of bleeding

Contraindications


P recautions

P regnancy


P recautions

Adjust dose in renal impairment

Sulfamethoxazole and trimethoprim (Bactrim, Septra, Cotrim)

Inhibits bacterial growth by inhibiting synthesis of dihydrofolic acid.

D osing

Adult

160 mg (trimethoprim component)/800 mg (sulfamethoxazole component) PO q12h (ie, 1 double-

strength tab q12h)

P ediatric


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2 months: 15-20 mg/kg/d (based on trimethoprim) PO divided q12h

Interactions

May increase P T when used with warfarin (perform coagulation tests and adjust dose accordingly);

coadministration with dapsone may increase blood levels of both drugs; coadministration of

diuretics increases incidence of thrombocytopenia purpura in elderly patients; phenytoin levels

may increase with coadministration; may potentiate effects of methotrexate in bone marrow

depression; hypoglycemic response to sulfonylureas may increase with coadministration; may

increase levels of zidovudine

Contraindications

Documented hypersensitivity; megaloblastic anemia due to folate deficiency; age


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asthma who have atelectasis of the right middle lobe during an acute asthma exacerbation and

in children with acute pneumonia of the right middle lobe to document resolution.

y Recently, a more aggressive approach in a cohort of 55 symptomatic children with right middle

lobe syndrome followed for a median duration of 2 years yielded good outcome. [3 ]All these

children underwent flexible bronchoscopy at presentation, and specific antibiotic therapy was

given based on bronchial alveolar lavage fluid. Bronchiectasis was documented in 27% of

patients, and the duration of symptoms correlated with the development of this unfavorable

complication.

Complications

y Long-term complications range from none to minimal pulmonary scarring of no discernible

physiological consequence to severe bronchiectasis requiring surgical intervention.

y In children with asthma, right middle lobe syndrome may produce a vicious cycle of infection,inflammation, and asthma exacerbation.

P rognosis

y Right middle lobe syndrome resolves in approximately 33% of children after bronchoscopy.

Approximately 33% recover eventually with medical management, 22% require lobectomy, and

11% have decreased severity of symptoms but should be monitored for the possibility of

requiring lobectomy later.

y About one third of patients with right middle lobe syndrome in early childhood continue to have

symptoms in later childhood. These patients usually experience asthma symptoms or another

chronic lung condition such as cystic fibrosis. A recent study examined the efficacy of early

postnatal corticosteroids for preventing chronic lung disease in preterm infants. [4 ]

y The remaining two thirds of children with right middle lobe syndrome do not have persistent

symptoms later in adulthood.

P atient Education

y Because chest physical therapy and postural drainage are of paramount importance in the

management of RMLS, instruct the caretaker with appropriate techniques and position for right

middle lobe physiotherapy. This is often performed by a registered respiratory or physical

therapist. Regardless, the therapist should be somebody who frequently deals with children.

y Flutter valve and high-frequency oscillation (known as the vest) have not been studied in this

setting, but they may be alternative modalities of delivering chest physical therapy.

Miscellaneous


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Medicolegal P itfalls

y The vague nature of right middle lobe syndrome (RMLS) symptoms may lead to a delay in

diagnosis. Approximately 10% of children admitted for acute asthma have atelectasis of one or

more lobes; the right middle lobe is most commonly affected. Because of the high incidence in

children with asthma, if chest radiography suggests right middle lobe atelectasis, another chest

radiograph should be obtained 3-4 weeks later to document total resolution. Early detection

and aggressive initial management may alter the course of this disease.

y Too often, right middle lobe syndrome is mistaken for an acute pneumonia and is simply treated

with antibiotics, without a follow-up radiograph. This underdiagnosis with resultant

undertreatment can be harmful to the underlying lung.

Multimedia

Media file 1: P osteroanterior chest radiograph demonstrating right middle lobe collapse and

infiltrate. Note blurred right heart border.


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Media file 2: Lateral view chest radiograph of Media file 1 showing a wedge-shaped density

extending from the hilum anteriorly and inferiorly.

Media file 3: Chest CT scan showing extensive bronchiectasis of both medial and lateral segmentsof the right middle lobe.

Brock Syndrome

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