How is lung transplant rejection graded?

Updated: Jun 06, 2019
  • Author: Aliya N Husain, MBBS, MD; Chief Editor: Philip T Cagle, MD  more...
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The incidence of acute rejection is low with current immunosuppressive regimens, but chronic rejection remains the main complication that limits long-term survival. [1, 2] The International Society for Heart and Lung Transplantation (ISHLT) grading of lung transplant rejection was updated in 1996 [4] and revised in 2007 [5] (see Table 1). Grades B and C are simplified in the latter; however, many clinicians and pathologists still use the former system because it offers more information on which treatment decisions can be based.

In 2018, the ISHLT proposed a grading system for lung posttransplantation airway complications in adults and children that includes ischemia and necrosis (I), dehiscense (D), stenosis (S), and malacia (M). [6]  These categories are further subdivided by location (all) and extent (all but malacia). [6]  (See Table 2, below.)

Table 1. ISHLT Grading of Lung Transplant Rejection—1996 and 2007. (Open Table in a new window)



A. Acute Rejection

A. Acute Rejection

A0 - Normal

A1 - Minimal

A2 - Mild

A3 - Moderate

A4 - Severe

Grade 0 - None

Grade 1 - Minimal

Grade 2 - Mild

Grade 3 - Moderate

Grade 4 - Severe

B. Airway Inflammation

B. Airway Inflammation

BX - Inadequate sampling

B0 - None

B1 - Minimal

B2 - Mild

B3 - Moderate

B4 - Severe

Grade 0 - None

Grade 1R - Low grade*

Grade 2R - High grade*

Grade X - Ungradeable

C. Chronic Airway Rejection - Bronchiolitis obliterans

C. Chronic Airway Rejection - Obliterative bronchiolitis

a. Active

b. Inactive

0 - Absent

1 - Present

D. Chronic Vascular Rejection – Accelerated graft vascular sclerosis

D. Chronic Vascular Rejection – Accelerated graft vascular sclerosis

*”R" denotes revised grade to avoid confusion with the 1996 scheme.

Table 2. 2018 ISHLT Proposed Grading System for Lung Posttransplantation Airway Complications [6] (Open Table in a new window)




Ischemia and Necrosis (I)

a. Perianastomotic: Within 1 cm of the anastomosis

a. < 50% circumferential ischemia

b. Extends 41 cm from the anastomosis to the major airways (bronchus intermedius and distal left main stem)

b. >50%-100% of circumferential ischemia

c. Extends 41 cm from the anastomosis into the lobar or segmental airways

c. < 50% circumferential necrosis


d. >50%-100% of circumferential necrosis

Dehiscense (D)

a. Cartilaginous

a. 0%-25% of circumference

b. Membranous

b. >25%-50% of circumference

c. Both

c. >50%-75% of circumference


d. >75% of circumference

Stenosis (S)

a. Anastomotic

a. 0%-25% reduction in cross-sectional area

b. Anastomotic plus lobar/segmental

b. 25%-50% reduction in cross-sectional area

c. Lobar/segmental only

c. 50% to < 100% reduction in cross-sectional area


d. 100% distribution

Malacia (M)

a. Perianastomotic: Within 1 cm of the anastomosis


b. Diffuse: Involves the anastomosis and extends beyond 1 cm


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