Cough is defined as a forced expulsive maneuver against a closed glottis and is associated with a characteristic sound [1].

Acute cough is defined as a recent onset of cough lasting <3 weeks; chronic cough is one that lasts >8 weeks [1, 7].

Prolonged acute cough resolves over a 3- to 8-week period. An example is Pertussis cough, which may need an additional period of time to elapse before further investigations are performed.

Recurrent cough refers to repeated (>2/year) cough episodes not related to head colds, each lasting >7–14 days [8, 9]. It can be difficult to distinguish from persistent chronic cough. Most simple infective causes of cough resolve in 3–4 weeks. Children with chronic cough may require further investigations.

Based on the suggested etiology, cough can be categorized as “normal” or “expected” cough, specific cough, and non-specific cough (Fig. 1). “Normal” children cough 11 times a day on average, although some children experience more than 30 episodes a day, as shown in recent studies [10, 11]. Frequency and severity increase during upper respiratory tract infection, which occurs in more frequently in the pediatric age group than in adults [1, 2].

When there are symptoms and signs that point to a certain diagnosis, thus demanding further investigation, cough is defined as specific.

Non-specific cough describes cases in which cough — usually dry — is the only symptom (isolated cough) and the child is otherwise well. Most cases are thought to be post-viral and related to increased cough receptor sensitivity [12, 13] and less likely to asthma or gastro — esophageal reflux [1].

Acute cough is most commonly caused by viral respiratory tract infections [14], which may or may not be associated with acute bronchitis. Other causes include seasonal allergic rhinitis, hay fever, an inhaled foreign body, and the first presentation of a chronic disorder.

According to British Thoracic Society guidelines [1], if acute cough is due to an uncomplicated upper respiratory tract infection (absence of fever, tachypnea, and chest signs), no further investigation is needed. If an inhaled foreign body is suspected as the cause, then an urgent rigid bronchoscopy should be performed. A chest radiograph is considered when lower respiratory signs are present (Fig. 2), when there are hemoptysis, or the suggestion of a chronic respiratory disorder or when a cough is relentlessly progressive beyond 2–3 weeks.

There may be an overlap between recurrent and chronic cough, which is why for investigation purposes these categories, along with prolonged acute cough, are not separated. Most children with chronic cough have recurrent viral bronchitis or post viral syndromes (subacute cough).

Causes of chronic cough may be classified in two groups [15]: (1) chronic isolated (no wheezing) non-specific cough in an otherwise healthy child and (2) a chronic cough in which the child has a serious underlying lung condition (Table 2).

A chest radiograph is indicated for most children with chronic cough, unless there is also a minor identified disorder, such as asthma or allergic rhinitis (Table 4). Spirometry should be always attempted in children capable of performing the maneuvers (generally those over the age of 5 years) [1, 2].

In children with a specific cough, further investigations may be warranted (Figs. 3, 4), except when asthma is the main cause [1, 2]. The next sections discuss the various etiologies of chronic cough.

Sinusitis is a very common condition in children. Chronic sinusitis (lasting >3 months) involves symptoms that include nasal obstruction, nasal discharge, halitosis, and headache [16]. Although some authors report a high incidence of incidental sinus opacification in children [17], those data may be biased by different interpretations of mucosal thickening and by the true health condition of the population included in such studies [18]. Tatli et al. [18] found a 52% prevalence of moderate to severe opacification of the paranasal sinus on computed tomography (CT) in children with chronic cough, with 90% involvement of the maxillary sinuses.

Radiographs are used as a screening method for pathological conditions involving the sinuses but CT remains the imaging modality of choice for the evaluation of acute and chronic sinus inflammatory processes [19]. The association between adenoidal hypertrophy and rhinosinusitis with upper airway inflammation is increasingly recognized, with one study [20] stating that magnetic resonance imaging (MRI) can document changes in adenoid size associated with the resolution of rhinosinusitis (Fig. 5). Further studies are necessary to define the role of MRI in adenoidal hypertrophy.